Item: Black Sludge. EV Spread: 252 Spe, 252 HP, 4 Atk. Nature: Jolly (+Spe, -SpA) Ability: Inner Focus
I'm going to start out by saying that this moveset is VERY different from your average Crobat. You may think it terrible and weak but give it a chance before you talk down on it. It generally works for me and you're welcome to try it also.
Haze - Prevents your opponent from raising his or her stats to become an unstoppable force.
Defog - Takes away annoying Switch Hazards and lowers your opponents evasion if you want to use a move that requires more accuracy.
Cross Poison - Great STAB move with a higher chance of critical and the chance to poison your opponent
U-Turn - Predict your opponents move and switch out to a type that it will not effect. Plus, it's a generally good move for Crobat in general.
This Crobat isn't set up to be a last resort or to be a great attacker. I always use Crobat first and U-Turn to try to predict an opponents moves and to keep Crobat alive for when I need him.