Legs, perhaps an unpopular choice

Probably legs and thighs and sometimes arms.

is there a pee muscle?

My jaws and tongue, with pie

Biceps and triceps. I've also exercised my abdominal muscles, but I haven't done that in a long time. If you have a fat belly and you grow your abdominal muscles, it just makes you look fatter.

My favorite muscles to (s)train are my ciliary muscles

Arms, legs.

Leg day, all day. Gives me a nice tone buttocks 😁😉

The one between my ears.

Neck 😏

Brain

Shoulders

Heart.

The only muscles I train are whatever is involved in cycling. Thinking about getting a gym membership tho