Well as cliche as it may be... I think Man is the deadliest animal...
so If I were the ballsy type in a situation with yeerks.... I'd be a Man, with a bottle of Bourbon, dissociative issues, horrible anger problem, with a spas 12....
However, since it IS ANImorphs... I guess animals are needed.
Land-Silverback gorilla ( what can I say... I like punching people)
Sea-Megaladon...look it up
Air-Golden Eagle