Cooking! I'm not a weird loner with a fire fetish, I'm channeling my inner Francis Mallmann. No really, if you get really serious about it, cooking can be a great solitary, hyperfocus, hobby. From distilling my own sea salt to cataloging where to harvest wild fennel and clams, it's not something I'd want to do in a group.

And, you do get to have people over in circumstances you completely control!