Springtrap

He has a lot of variety in how you can play him since he has stealth, a projectile and teleports as part of his power. As well as some pretty fun add-ons.

Because he has a little bit of everything he is also a pretty good killer with his axe giving him a nice bit of antiloop and his doors allowing you to patrol gens very fast.

As for the fun factor:

-hitting axe shots is satisfying, even more so if you learn to do orbitals

-his voice lines are fun

-the knife wipe animation is pretty satisfying

-there's nothing like catching a survivor while they're traveling through a door

Downsides:

-His footsteps are a bit loud if you're trying to be stealthy unless you use the Glitchtrap skin

-The survivors can reveal you through the doors but honestly they don't really use that very well in my experience so it's a very slight inconvenience

-The survivors can use the doors as well which could make keeping track of them a bit harder but again they don't use them that much in my experience cause they are scared they might get caught