In my Fantasy games I almost always run a couple spawn. They are good humor, they look cool, and quite often do the unexpected. The spawn kit is one of my absolute favorites. You can create a regular old spawn like this one.
Or do something else with all of those cool parts, and a bit of creativeness.
In this case, a chaos troll and an ogre head. I really dislike the troll bodies, but with a dremel and a bit of GS work I think they make really cool looking spawn.
Both of these will be in my Warriors of chaos army. They'll be fun to paint.