De-bugging The System
Venomoth is unique since, other than Yanmega, it is the only Pokemon who can use the ability Tinted Lens. This allows Venomoth's shallow movepool to bypass the conventional shielding of "it's not very effective", doubling the power of resisted hits. That, along with its decent Special Attack and Speed, makes the bug a usable Pokemon.
Here's the best way to exploit Tinted Lens:
Venomoth @ Choice Specs
6 HP / 252 SpA / 252 Spe
~ Bug Buzz
~ Sludge Bomb
~ Sleep Powder
Bug Buzz and Sludge Bomb together make a good combo, only being resisted by a handful of Pokemon. Psychic handles some of Venomoth's common threats, such as Nidoking, Nidoqueen, and Tentacruel. Finally, Sleep Powder can put the rest of Venomoth's counters out of commision. Of course, if you don't feel comfortable using a status move in conjunction with Choice Specs, you can replace it with HP Ground or HP Fighting.
Ballom's Rating: 3/5. For its wonderful ability, Venomoth is too slow and fragile (in comparison to many OU Pokemon) to be used to any great effect. Still, it can be fun to use, on occasion.