After having worked on keyboards, drum machines, synths, samplers, as well as a few toys, I have more recently specialised on FX devices. Instruments that are made to produce sounds on their own tend to have a distinct sound that can get quite tiring after a while. Multi effects, in my opinion offer a wider range of possibilities because they can process whatever you put through them. Also, once they are circuit bent, there's ways of making them produce sounds on their own that are a lot more organic than most other circuit bent gear.

Kaoss Wad KW2  Waoss Pad   ZOOM SOS  Linguaphone  Yamadore SHS-10  DR Link  Casio VA-10      Linetomic  tr505