Have you tried wood carving? Just a few relatively inexpensive tools, easy clean up, no chemicals or anything that can spill unless you want to finish the wood. Many projects can be done hand-held. Model airplanes or cars need little space and it's not expensive. Just make sure you have plenty of ventilation if you're painting gluing.
Wanted to suggest wood carving and model-airplanes (or similar stuff) but Brian Wolfe beat me to it.
Still: pencil drawing, any kind of magic tricks (including card tricks), playing a musical instrument (though your neighbors might object), origami, collage\ assemblage, collecting stuff (coins, stamps, buttons, stones - why not?), learning to code/ model/ texture/ etc. (if you're into computers)...That's about all I can think of at this rate.
Edit: Oooh, and as someone suggested on the forum here - knitting/ sowing/ embroidery, and that sort of stuff. Sure, it might not be the manliest thing out there, but it's good when you're bored or anxious, and actually quite useful - DIYing and repairing clothes :)
Knitting. Fighter pilots find it very useful.
Knots - many to learn.