Short answer: my usual suspects are a Wurlitzer, a Little Phatty or a Septavox. Electric guitar or bass come right after. Options and screens will get me out of the flow.
Long answer…
To me the answer is related to how limited the said instrument is. I find myself way more intuitive when the instrument does not offer a plethora of options. That being said, I find myself limited on non-chromatic instruments: I prefer having those 12 notes
When it comes to electronic instruments, another crucial point to me is how familiar I am with the instrument interface: manipulations should be immediate and I like very much this feeling of the instrument “understanding” where I want to take it. For analogue instruments, in particular, parameter calibration can be a criterion too.
An effect pedal or two can help but more than that will get me into the brain area, so will any sequencer related instruments, like my beloved MachineDrum (even if I speak MD fluently) most probably because I need to relate a movement to an immediate change in sound vs a change in the pattern or whatever is “programmed”. The worst being a computer.
Hope this helps