Knitting has the advantage that you can do it anywhere and at any time without 'bothering' anybody else. Sitting on the bus, watching TV, having a conversation. Most people I know who knit use it almost as a 'fidget toy' that they're subconsciously playing with while simultaneously doing something else. Only looking down every few minutes or so to make sure they're on the right track or to make some change

I recently picked up an analog drum machine - Arturia Drumbrute Impact. I play guitar a little already and picked this up to play some industrial music. It's turned out to be a such a fun device on it's own I'm considering picking up a bass machine, sequencer, and synth.

I can totally zone out creating and tweaking beats on the Drumbrute Impact. I also find it oddly comforting to have on when I'm working.

No better time in history to learn guitar. Amazing online resources, the world is flooded with cheap guitars as well if you’re happy with 2nd hand. There is a technical side to it (tuning, restringing) and plenty of toys, pedals and computer integration to any nerd hearts content. Even if you get stuck at 3 chords it’s amazing the number of pop songs you can suddenly play. Plus if you get past there you still have classical, jazz or whatever super hard path you want to travel to explore.

Guitar definitely. An acoustic guitar is ideal since you just pick it up and start playing any time (even plugging something in can be a barrier sometimes). My rule is I always play for 10 minutes minimum every day, even when I'm not feeling it.

The great thing about guitars is that you can buy really well made ones, brand new, for only $100-300. That and a $10 tuner and watching free online tutorials is all you need.

I agree, musical instruments also have the benefit of a much higher skill ceiling. That can also be a downside though, since it can make it frustrating to learn