I really enjoy photographing old rail cars and engines. There's just so much detail and texture to explore, and there are often really cool signs and logos as well. Plus, they move, so they're always (okay, often) in a new place, new scenery, new lighting. Or, it could be I'm just a big dork who likes trains. Whatever.
This is one of the South Shore interurban cars at the Fox River Trolley Museum. They're not currently operative (thus missing on the whole moving thing) but they are eminently photogenic.