The god honest truth to that question is an unpopular one: there is no top 10 Pokemon. Because Game Freak's clientele is so vast and varied, chances are you could probably make any combination work at least once -- if you're artful enough, at least. But there are, however, Pokemon which are way more popular than others, Pokemon many see as far superior than the rest. Which ones exactly? Well, depending on the time of day or who you ask, the list could vary but since you're here, I'm going to assume you want to know which Pokemon I think are the best. Be advised: I'm keeping the legendaries exempt from the list because, god damn, they can be infuriating to snag. Anyway, here's my list of the top 10 best Pokemon you can use for pulverizing other unsuspecting cotton-candy monstrosities. Enjoy, you animals.
Before anyone asks, I actually love Aegislash's design. Sure, it might yet be another sapient piece of equipment but a haunted sword? Who wouldn't want that accompanying them on their Pokemon journey? The Steel/Ghost type is immune to Normal, Poison and Fighting. Additionally, it takes a quarter damage from Bug types and is resistant to Flying, Rock, Steel, Grass, Psychic, Ice, Dragon AND Fairy. Which, all things taken into consideration, sort of makes up for the fact it's susceptible to attacks from Ground, Ghost, Fire and Dark.
But while it has laudable typing, Aegislash's popularity primarily hinges on its stances and King's Shield. In a nutshell, Aegislash begins every match in Shield Form, which provides an impressive 150 base defense and 150 special defense. It is only when you choose to have Aegislash go on the offensive does it switch to Sword Form, swapping its high defense for high attacks. King's Shield makes things even more interesting for Aegislash. A Steel-type move, King's Shield protects from all physical and special moves, drops the opposition's Attack should they come within contact with the Aegislash, and reverts Aegislash back to Shield Form. Best of all? King's Shield always goes first in every round.
There's more to Aegislash, of course, but everything else is pretty much window dressing at this point.
There is unpleasant and there is so absolutely offensive you need to kill it on sight. Greninja is a crowd favorite not because he's the frog ninja with a tongue scarf but because of one crucial ability: Protean. Protean is, to put it mildly, totally bonkers. It's an Ability which changes Greninja's typing to fit any move it currently is using. In short, STAB attacks everywhere. Everywhere. The fast-moving amphibian, who rocks one of if not the highest base Speed in the game, basically deals 1.5x damage with, well, everything its arsenal. To make matters worse, you can also utilize Protean defensively. Raichu looking to cook itself some frog legs? No problem! Go ahead and Grass Knot it up. Laugh at the Thunder Bolt Greninja is a nightmare waiting to happen, a flexible frog who can be easily used to lead a furious charge against the opposition as either an offensive Sweeper or a damage-over-movement-dealing Spiker. But mostly as a sweeper. Good god, he's a nasty sweeper.
(Note: The Pokemon in question does have appalling defense and negligible typing. Don't expect it to tank, well, anything.)
Okay, okay. There's no delicate way of putting it. Mega Mawile's a bit of a cheap bastard. The Steel/Fairy, which naturally enjoys some killer resistances, is a brick wall and Chuck Norris rolled into one. With Swords Dance in its arsenal, Mega Mawile can potentially dole out some catastrophic amounts of damage. How? A high base attack combined with the attack-doubling Huge Power and shameless abuse of Sucker Punch, that's how. To make things even worse for the opposing Pokemon, Mega Mawile is armed with pretty solid defense.
Grousing aside, what's really great about Mega Mawile is the simple fact that it isn't necessarily broken. Against a newbie, chances are the innocuous-seeming Pokemon will probably break faces -- especially if it's allowed to run amok and Swords Dance to its heart's content. But Mega Mawile's weaknesses are easy enough to exploit. Fire and Ground aren't uncommon to find on the battlefield. Combined with Mega Mawile's shrug-inducing Special Defense, laughable Speed and a handfu of other variables, it makes it far from impossible to control Mega Mawile's onslaught.
And also way more fun for the Mega Mawile's owner too. (Do you really want to play something that can one-shot everything on sight? Really? Do you? Or do you want to build strategy? Hmmm? Hmmmmmmmmm?)
If there's anything that Drinkbox Studios' Guacamelee has taught me, it's that no game is complete without a luchador. There are plenty of reasons as to why you might want to pick this plucky poultry, the first being the fact it's immune to one of Flying's worst enemies: Stealth Rock. Hawlucha also enjoys access to Limber, Unburden and Mold Breaker. The first keeps it safe from paralysis, the second allows Hawlucha to double its already ridiculous speed while the last permits it to ignore another Pokemon's abilities. (See: Dragonite's Multiscale) The hard-hitting Hawlucha, which usually banks on its high attack and speed, is capable of running some massively awesome movesets. One of the Internet's favorites in this department is one that includes a Hawlucha with Unburden, Swords Dance, High Jump Kick, Acrobatics and Sky Attack.
The last is probably most interesting, by the way. Sky Attack, which counts as a STAB move for Hawlucha, is ordinarily a two-turn move. But when used in combination with Power Berry, it can allow Hawlucha to deal a devastating attack and trigger its speed-increasing Ability all at the same time. Oh, and Flinch sometimes happens too. Nice, eh?
Rotom Wash is not only a mean customer on the battlefield, it's murder on tough stains. The possessed washing machine is the embodiment of practical bad-assery: it produces fresh linen, fresh wins and fresh tears on your opponents' faces. Jokes aside, though, Rotom Wash really is quite snazzy. Much of it has to do with the bionic bogeyman's excellent Electric/Water typing. Though Rotom Wash doesn't enjoy a gratuitous amount of immunities, it makes up for that inadequacy by having only a single weakness. One! Like Achilles except with mechanical parts. On top of that, the haunted household appliance is also resistant to Flying, Steel, Fire, Water and Ice.
Stats-wise, Rotom Wash is neither awe-inspiring nor terrible; just strong enough to function as a good wall. The Electric/Water Pokemon can, however, wreck madness with its ability to fire souped-up Hydro Pumps, Thunders and Volt Switches -- making it the kind of scout every army wishes it had. (Instead of those skinny pansies who can only snoop around and not deal maddening amounts of damage and chaos.)
Help, oh god. Help. As if it wasn't enough to be stalked by a fat ghost with a Joker-esque grin and a penchant for hijacking your shadow, Game Freak had to give the portly poltergeist a Mega Evolution. Mega Gengar, even if it resembles a malevolent tooth, is such a terrifying bastard that Smogon's OU Council elected to quickban Gengarite (which allows for Mega Evolution) from their games -- which kind of tells you precisely the kind of terror Gengar's Mega Evolution is. But because we're here for specifics, let's take a look at all the ways this ghost is broken after you've stuffed an innocuous rock into its stubby hands.
To begin with, Mega Gengar's immune to Normal, Fighting (Ha, Hawlucha!) and Ground. It's also resistant to Poison, Bug, Grass and Fairy. While susceptible to things like Dugtrio and Espeon, Mega Gengar's enormous move pool(Destiny? Will o'Wisp? Taunt? Got 'em all!), and access to Shadow Tag offer savvy trainers the ability to lock down and kill virtually anything outside of another Ghost-Type.Like, it's not even implicated. That's the precise reason as to why even the mere mention of Gengarite is enough to trigger Post Tramautic Stress Disorder in certain Trainers.
Land shark? Land shark. Land shaaaaark. Ignoring the questionable color scheme, Garchomp's really one of those Pokemon that all but RSVP a position in any top 10 list. Once again, typing serves as one of the primary reasons for Garchomp's prevalence in the competitive arena. The unusual Ground/Dragon typing keeps it safe from the predation of Grass and Water Pokemon, the traditional enemies of Ground types. It is also resistant to Poison, one of Dragon's worst enemies, (Stealth) Rock and Fire. Granted, the trade off includes having to deal with an astounding vulnerability to Ice but it's strangely worth it. In addition, Garchomp sees fantastic overall stats. Nothing that makes it the best of a class but it's a solid distribution few trainers can complain about. That said, Garchomp's best attribute is simply its versatility: great STAB attacks, access to a decent move pool, and that ridiculous Sand Veil, which allows it to increase its evasion rate even in enemy Sandstorms.
A parent's love knows no limits. Which is probably why Parental Bond is so very beastly. Much can be said about the unassuming-looking Kangaskhan. Cuddly. Adorable. Nondescript. Far from being the coolest Pokemon the block. But while it only elicited shrugs in previous Generations, the introduction of Mega Kangaskhan in Pokemon X & has made this family-minded Pokemon catapult in popularity. As is often the case, a big part of Mega Kangaskhan's appeal is tied to its signature ability. Parental Bond is deceptively simple; it lets Mega Kangaskhan hit twice (the second attack operates at 50% effectiveness) with any single-target move.
Things get even more interesting when you begin dissecting the implications. Fixed-damage moves, for example, will hit for full strength both times. Stat-boosting techniques like Power-Up Punch will raise the appropriate stat twice. All said and done, Mega Kangaskhan, who has some pretty solid defensive stats to boot, is one of the rare Pokemon can easily one-hit KO most non-legendaries. Plus? Cute baby in tow. Always a bonus.
Who would have thought that something so very, very cute could be such a menace to competitive society? Togepi's final form can rock a wide variety of roles though its' excellent base special attack and defense make it a reliable special attack sweeper. Happily, Togekiss's versatility is also another reason to delight in its company. Enemies will waste time musing about whether the Togekiss you just swapped in is on the offensive or a tankier, more solid threat.
Seriously, though. Togekiss is pretty rock solid in spite of not being a Rock type. With the Serene Grace ability, Togekiss may potentially benefit from a 60% Flinch chance when using Air Slash which, coincidentally, would be a STAB attack in Togekiss's arsenal. Throw in moves like Nasty Plot, which raises the Pokemon's special attack, and Tri Attack, which can potentially inflict serious status effects, and you'll have yourself an egg-cellent Pokemon.
Klefki is infuriating, if for no other reason than the fact tbat such a sloppily-designed Pokemon has no business being so damned useful. But in spite of looking like a last-ditch effort to fulfill this generation's quota of new Pokemon, this sentient household fixture is the key to many a-successful Pokemon team. (See what I did there? See what I - Ugh. I'll stop.) Being Steel/Fairy, our jangly friend is immune to the bane of poncy pixies everywhere: Poison. It's also impervious to Dragons, making it ideal against the still-fearsome-but-not-quite-as-terrifying reptiles. If that wasn't enough, Klefki's dual-typing allows it a resistance against Normal, Flying, Rock, Bug, Grass, Psychic, Ice, Dark and other Fairy types.
Asides from having strong defensive capabilities and Prankster (which increases the priority of its status moves by one), the floating keychain is privy to two signature moves: Fairy Lock and Crafty Shield. Both rock. The former is a killer setup; it prevents all Pokemon from escaping the next turn. The latter protects both the Klefki and its allies from being targeted by irritating status moves like Charm. (You'd still get thumped by status moves which cause damage, but, the Klefki can't lock down on all possibilities, eh?)
It can turn into Mewtwo and assist you with all the breeding you require. In terms of sheer utility, Ditto wins all.