What kinds of sea stars are there that harlequin shrimp won't eat?

Harliquins will NOT eat serpent / brittle stars. If its a slow moving 'standard' style of star like how the chocolate chips are, consider it shrimp food pretty quickly.

Brittles are so fast and always try to escape, where as normal sea stars clamp down when attacked and dont move. Probably has the most to do with it.

Read this:
http://www.chucksaddiction.com/harlequinshrimp.html