@ Mega Kanga - I always beat it by running something faster than it that resists Sucker Punch. Alternatively, beat priority with priority, which makes Sucker Punch completely null. Off the top of my head, there's M-Lucario, Blaziken (even regular) with Speed Boost/Protect, Weavile (assuming they'd want to outspeed you/have prior damage, or you have a Swords Dance/CB boost), Mienshao (even if they have a Ghost-type switch-in, Regenerator ensures it'll live long enough to keep that Kanga checked), Unburden Hawlucha/Hitmonlee (personally I'd run a Kee Berry then switch in to a predicted Crunch/SP, or a Normal Gem + Fake Out in Hitmonlee's case. The latter also gets Mach Punch), Protect/Sub/Disable M-Banette (completely walls it if it has Will-O-Wisp), a phazing bulky wall (Steelix or Aggron with Dragon Tail/Roar come to mind), bulky/DD M-Gyarados (combination of Intimidate/predicting whether or not they'll Mega Evolve, as Power-Up Punch isn't effective against regular Gyara, and M-Gyara resists Sucker Punch), and so on.
Additionally, once Pokebank comes out, it'll be completely useless against the Muske-deer trio (especially since Crunch effectively gives a Swords Dance boost to anything with Justified), Infernape, Weezing (immune to/resists EQ/PoP, just bulky enough to live through Return and Will-O-Wisp it back), a bunch of other priority users (Extreme Speed Dragonite and Whimsicott come to mind, the latter with new Fairy typing which allows it to resist both Dark moves and Earthquake, plus has Prankster to annoy the crap out of it). All in all, it's good, but I don't think it's Uber (even though it shines in Ubers as well).