For Animal I think Backstabber by far
For Cannibal I think Cannibal would have been interesting with the right promotion, may have even gotten a bit of controversy to boost it. (Not promo single mind you, actual single)
For Warrior I've always thought All That Matters (The Beautiful Life) would have been a perfect way to end the era. Not saying this is my favorite song on the album, but at the time Kesha still would have been seen as a party girl. So it wouldn't shock the GP too much
Unreleased-wise I think WooHoo would have KILLED it