ST: I like Funhouse. Classic "easy to learn but hard to master" game. Mine also has a CC playfield so it plays pretty brutally compared to other ones I've played.
LT: STTNG. I may take a break from it but I always come back. Do you want to go to Final Frontier? Do you want to play or time out the modes? Do you want to rip the super spinner? Do you want to play Borg multiball? Maybe you want to rack up ramp millions. There are so many ways to play it that it never gets old for me.