MPC500 and recently Electribe Es-1.
Electribe is somewhat limiting in the way of time signatures/loops but has a very smooth interface for recording directly into the machine...complements the MPC by providing a base rhythm to guide my terrible sense of timing in sequence mode.
The sequencer can make for some very blown-out improvisations via layering to infinity...only catch with the MPC is the terrible onboard sample editing, which pretty much necessitates the use of a computer.
