I'll second the ramps on Taxi and even Fishtales. It's pretty fun to get in a groove and alternate ramps.
Also the bendy ramp on Cyclone is fun.
Creech has some pretty crazy ramp action, but I'm not sure if I'm sold on it.
Mousin' Around has a ramp that diverts the ball into the "mouse hole" behind the playfield, and then ejects it back on the right into a bendy ramp like the one in Cyclone, that's pretty fun and unique. It also has the middle ramp / return that you have to complete targets to make available, and that one's kind of fun to shoot.