I have an M-Audio Axiom 25, which is great for getting parts in, auditioning patches, etc. It's my go-to controller for almost everything.
If I feel like really going crazy on the keyboard, I have an old Yamaha KX88 MIDI controller keyboard from the 80s. Weighs about 80 lbs, has weighted keys, many people say it's the best 88 key MIDI controller of all time. It's connected to the back of the Axiom 25 via MIDI so that both keyboards are being sent over the same USB cable to my G5.