I picked up a MicroKorg for a very reasonable price and haven't been able to stop playing with it since. As a classically trained pianist I always used to (internally) turn my nose up at these sorts of machines - how could you ever make something interesting with so few keys. The MicroKorg has 32 small keys, and it was initially quite difficult to get used to their size and hit notes accurately, but after spending time with it I'm loving it.
I play in a funk band and use a Wii Rockband controller as a wireless keytar (don't laugh), it's actually a great Midi controller and the wireless feature is a plus because I can wander around the stage. Anyway the first time I used it in a performance, I did my solo on the 32 key keytar instead of my usual 88 key keyboard, and the restriction, instead of limiting my options, opened up a world of opportunity. Normally with these solos I fumble about the blues scale using vague, fast runs to compensate for lack of imagination, but when confined to a small set of keys I came up with something new and interesting.
I think something similar happens when I play the MicroKorg, its limitation is not actually a limitation, but an opportunity. Plus is has a huge range of sounds, being a digital synthesizer. You can combine various oscillators, filters, envelopes, LFOs, and much more to create a massive variety of noises, from classic synth sounds to Hammond Organ-esque tones. The vocoder has huge potential.
This inspires me to try and make an analogue synth (the MicroKorg is digital).