Crobat
Ability: Infiltrator
EVs: 248 HP / 124 Def / 136 Spe (Outspeeds base 115s and below, the most important Speed benchmark for Crobat to hit)
Jolly Nature
- Acrobatics
- Super Fang / Defog / Toxic
- Taunt
- Roost
Enter Crobat, a mon often ridiculed for being bad in OU. While this is true to an extent, its actually fairly decent in practice. It has a great defensive typing, good bulk, and an awesome Speed tier. All of these traits enable Crobat to act as a decent stallbreaker akin to Mew, but with certain advantages over it. First and foremost, it lacks a Knock Off and U-Turn weakness, which leaves it less susceptible to being worn down when switching in. It also has a great 4x resistance to fighting, grass, and bug moves, which enables it to be a great check to mons like Keldeo while full out countering mega Venusaur. Finally, and most importantly, it has a toxic immunity, which prevents it from being stalled out by defensive teams, with the most notable being Heatran and certain lure mons. Furthermore, Crobat has super fang, which enables it to reliably beat any defensive mon bar Sableye guaranteed when used in tandem with taunt. It also has infiltrator, so mons like. Sub CM Keldeo and Celebi cannot get free turns like against many other Pokémon (Keldeo has a very small chance of living if it gets a single turn of lefties recovery. Otherwise it dies from the sub damage).
I'm not gonna sit here and say that Crobat is an amazing mon, but it does have uses for select teams that need a utility fairy check that isn't 4x weak to rocks or weak to flamethrower, while still putting in work against S rank mons such as Keldeo and Altaria.
Relevant calcs:
+1 192+ Atk Altaria Return vs. 248 HP / 124 Def Crobat: 119-141 (31.9 - 37.8%) -- 93.3% chance to 3HKO
+2 192+ Atk Altaria Return vs. 248 HP / 124 Def Crobat: 158-187 (42.3 - 50.1%) -- 0.4% chance to 2HKO
0 Atk Crobat Acrobatics (110 BP) vs. 0 HP / 0 Def Keldeo: 236-282 (73 - 87.3%) -- 81.3% chance to OHKO after 3 layers of Spikes
Heres a replay showcasing Crobat in action:
http://replay.pokemonshowdown.com/ou-219187771 <- This game was not on the ladder, but I can assure you that the guy I faced knows what he is doing.