My all time favourite still has to be my 170 keeper.
It's not nearly as fun since there are so few 170's around (it was built back when there was a 150-174 battlestation.)
But, I've had some other twinks that are pretty fun too.
I built a nice 85 enforcer with duel crispy's that is a lot of fun to play even in PVM. I use him a lot to destroy tiigs and help level orgmates.
I recently built a 90 MA with duel 145 kyr nunchaks that is kinda cool to play in PVP/PVT/PVM.
Some twinks I made that are/were less fun are a 55 soldier, an 86 soldier, a 100 enforcer, a 150 trader, a 150 neut keeper, a 170 advy, a 170 enforcer, a 110 trader, a 41 doctor, a 150 fixer, a 200 doctor, among others.
how bout you?