Geekiest Thing You Do Alone

I write code and listen to classical music, and sometimes play piano from sheet music.

I guess that's pretty geeky.

Im a linux nut so im constantly in fornt of my pc unless im sleeping

i not only watch the stargate tv show, but I RECORD it if I am going to miss it.
i read books about acoustic science.
i solder resistors and capacitors and all that crap.
i collect vintage champagne ads.
i smoke copius amounts of ganja while watching cartoons.

Straighten up the comics in the library, and worry that people are gonna mess them up with dirty fingerprints.
At home, I spend ages building cool houses on the Sims, then I chortle to myself as I burn them.

talk to my food. for example, singing to my baking potatoes while jabbing holes in them. "Big juicy potato.... just juiced in my eye..."