It depends on what you want to use it for.
I shoot landscapes and use a Manfrotto 405 geared head, this enables me to make precise adjustments to, for example, level a horizon. It would however be shocking to use for birdwatching!
Your main choices are a three way head (precise but a little cumbersome), a ball head (a good all rounder usually), a pistol grip head (a variation on a ball head with quicker adjustment) and then all sorts of specialist heads like panoramic, gimbal etc.
Tripod heads are, on the whole, universal fit, so you can find a head to suit you regardless of which legs you use.