1. gator gar - huge and toothy just look at a picture of a full grown one and then say you'd want to be a fish near it...let alone a person in water with one.
2. arapaima gigas - also huge, and they may not be toothy but anyone who has seen the slow motion shots of their vacuum style of eating must admit respect for them as a predator. plus as long as they've survived they're doing something right
3. giant snake head - big, mean, toothy, and if that isn't enough the ability to crawl on land for a bit.