Some staples in the current meta include:
Rotom-W, Tanky, only weakness is grass (which is pretty rare). Does alot of damage with its STAB moves Hydropump. Can volt switch for great momentum. Has great stat distribution and good movepool. Poplar setup is Chesto-Rest w/ Will-o-wisp to shut down physical attackers and thunderbolt and hydropump for damage.
Gliscor, Tanky, can do a variety of things such as toxic sub stall or baton pass buffs like swords dance. can also do alot of damage using stab earthquake.
Scizor, Still an amazing pokemon, not changed much from previous gens. Choice band bullet punch still hurts alot. Can also mega evolve and sweep pretty easily as well. Uturn gives great momentum
Kangaskhan, Mega evolving him is ridiculous. Double boost from power up punch, everything is pretty much at a +1 boost, can easily break subs because of his double attack. Has fantastic base stats, is tanky and fast too.
Ferrothorn, still great, is one of the best hazards setters because it is one of the few pokemon that can learn both spikes and stealth rocks. Great counter to mega kanga, esp if you throw a rock helmet on him. Tanky and can stall well with leech seed + leftovers
Tyranitar, with assault vest, tyranitar has become a even bigger monster than he already was. You can easily tank 2 or 3 hydro pumps from rotom-w with investment into HP only. He is tickled by non super effective special moves. High attack lets him retaliate and do alot of damage.
Talonflame, Priority Brave Bird choice banded, pretty goddamn ridiculous. Huge damage potential, can run leftovers or some other item if you don't want to be locked into brave bird/flare blitz
Scoliopede, amazing buff passer now thanks to his new hidden ability, Speed boost. Can pass iron defense/swords dance to people as well as his speed boost. Great for setting up a sweep.
Goodra, the new 600 BST dragon. He is very tanky on the special side and is viable as both a tank and damage dealer. All 3 of his abilities are viable depending on how you want to build him. Has great movepool.
Noivern, pretty fantastic new dragon. infiltrator gets past subs, and he gets boomburst, a 140BP 100% accuracy bomb.
Klefki, a great new prankster pokemon. Fantastic dual wall setter or swagger+thunderwave user. Is very versatile.
Aegislash, a very interesting pokemon. I'm personally not a huge fan, but it is definitely very powerful. Alot of mind games while using this pokemon. has huge stats either defensively or offensively depending on his mode.
Mega Charizard Y, Still weak to stealth rocks, but his high base sp. atk and drought ability makes his special based fire attacks melt everything. OHKOs alot more than you would expect with just heatwave/flamethrower
Azumarill, now he has access to belly drum and aqua jet, he is a huge threat. Belly drum maximizes his attack (x4 from base) in exchange for loss of half HP. Aqua jet is a stab priority move. Even without the belly drum boost, aqua jet puts dents in alot of pokemon. Also has 100/80/80 base defenses so it can survive alot. Great defensive typing as well.
Greninja, a very interesting new pokemon, his protean ability changes his type to the move he just used, letting him get stab on everything. He can also set up toxic spikes as a lead, and has great base speed to do it with. His high base sp.atk with his stab bonus also lets him do a lot of damage.
Mega Mawile, now boasts the highest attack in the game. Sucker punch stops alot of things in their tracks. Iron head and play rough are great coverage moves that get stab as well.