Breloom
I think people should use Luvdisc. It has decent speed, alright Sp. Attack, and it's cute. Really underrated Water-type.
Anyway, I'd say that Lilligant is an underrated Pokemon. While it has a shallow offensive movepool (literally consisting of Grass moves, Hidden Power, Dream Eater and Round), it gets Quiver Dance to help it sweep through teams given the right circumstances (Grass resists being weakened or eliminated).