I had a friend that taught me some... interesting strategies on bloodbath. Dirty strategies. I forgot some of them. This one's my favorite:
Hatchery rush. Usually only works if you find your enemy early with your Overlord, but can be done otherwise. Works best against Terran. Build two drones and then make a Hatchery in your enemy's base. While it is building, make a Spawning Pool back at your base. He won't be able to kill it unless he uses most/all of his workers. Once the hatchery is about 3/4 finished, send three drones into his base and make three Sunken Colonies as quickly as possible. He will have a difficult time killing all of them, especially of you can micromanage well and send more workers.