Are you keeping a bare bottom or a sand bedded tank?
If it's a sand bedded tank, sand shifting star, sand dollar and narcissus snail are a good bet.
Other cleaning crews that are ideal are red legged hermit crab, abalone, turbo snails, tuxedo urchins and sea hare.
Do note that urchins and turbo snails are famous for knocking off frags or taking frags for a ride.
I won't take boxing shrimp as a clean up crew unless you're talking it eating left over food.