Here's a few sets I've been running:
Shuckle @ Leftovers
Ability: Contrary
EVs: 4 HP / 252 Def / 252 SpD
Calm nature
- Infestation
- Mud Slap / Shell Smash
- Rest
- Sleep Talk
Shuckle is infamous for having sky-high defenses, and this set really takes advantage of that. Infestation traps the enemy Pokemon and gives a damage-over-time effect, and Mud Slap lowers the target's accuracy, and they won't be able to switch out because of Infestation! Combine that with possible Toxic Spikes support from a teammate, and you have one annoying thing to beat. And then, when you start to get low on health, Rest just heals you back to full health! Sleep Talk makes this set even more annoying, because Shuckle won't be completely incapacitated. Alternatively Shell Smash can be run over Mud Slap; you sacrifice some synergy with your team in order to have more staying power. Flying Pokemon and Levitators give the Mud Slap set trouble whereas Kingdra and Haze users give trouble to the Shell Smash variant, and Mega Metagross, Skarmory, and Wish users can handle both variants. WARNING: Do not use this set against your real-life friends, or they will not be your friend for much longer. My sister
Chinchou111 described this set as "pure evil" when I used it against her.
Houndoom @ Focus Sash
Ability: Flash Fire
EVs: 252 HP / 4 SpA / 252 Spe
Hasty nature
- Counter
- Destiny Bond
- Will-O-Wisp
- Fire Blast
Hoo boy does this catch people off-guard. Due to Houndoom's -Def nature, physical attacks will deal a significant amount of damage to him, usually OHKOing if it wasn't for the Sash, which is a good thing because it means you can use Counter to attack for a HUGE amount of damage. Destiny Bond also catches people off-guard and sometimes allows Houndoom to get 2 KOs. Another cool thing about this set is, if you mispredict with the DBond against something slower, you can use Counter the next turn to take advantage of its low priority without expiring the Destiny Bond effect. If you have full HP with no hazards up, this thing stops Belly Drum Azumarill even once it gets going. Obviously it falls flat against special attackers and supporters, except for things weak to Fire which is why Fire Blast is there. All in all, an outside-the-box set if you want something really unexpected.