As justin mentioned, I have a lot of pants/shoes. While I wouldn't say I collect them (least not in the way a snearhead does) I do own a lot. I'll count tonight for teh lulz.
In the past I was really into NBA/MLB cards. Had a ton as a kid. Was pretty much the only way to haver a record of stats, least far as I knew. Got in CDs in middle/high school, illegal DLing and the ipod made that obsolete. Used ot have quite a beer stash (maybe 60-80 bottles at one point? Just got excited about craft beer), slowly drinking that down, as well as considering what to do with all of my brewery glasses I bought.
Once I move into a house (IE space), I can easily see myself starting to collect bikes. I enjoy fixing them up, trying out new stuff, etc... Think it would turn into my hobby.
@justin, used to be into keeping books but they just take up too much space, not into them as decorations, and outside of maybe 2 books I'll never reread them.