I've noticed that good photographers can turn almost anything into an interesting photo, so I nominate... beer.
For people who don't want to associate with beer, non alcoholic beverages will do.
If people think this isn't acceptable then my second choice is a popular contest choice: aircraft.
Edit: I just noticed that the weekly assignment on fredmiranda.com from two weeks ago was beer. What a coincidence. I got the idea from the beer bottle next to my monitor.