1. Proteus 2000 if you need a tone module...the samples used on it are very well programmed, there are TONS of drums, and you can expand it with inexpensive PCM ROM cards.
2. Access Virus C if you need a virtual analogue synth...I played with this one at NAMM and was absolutely floored by the kinds of sounds it makes. Think 'movie soundtrack'.
3. Akai Z-8 sampler...it's Akai, it interfaces nicely with a computer, and it's Akai. Did I mention that it's Akai? If you're dead keen on having the MPC-style pads, they now sell one as a controller.