Weird hybrids or just hybrids in general.
Weird colors and weird colored parts.
Perfect characters (you know, super buff, strong, all that stuff).
Canines, felines, dragons. I love them, though, so it's not like this is a bad thing.
Can take anything.
Can fit anything.
Can cum as many times as they need to.
Don't get tired.
Last extremely long.
Probably a few other things too, but eh. I don't feel like thinking too hard.