being a deal hound and a bit of a hoarder (I'm working on both, but it's never easy to pass up a great deal), I've got lots, several of which I've never used.
REI Stoke 19: school, biking, and dayhiking pack
Stoke 9: biking, running in cold weather
Jam 2 ('09): multi-day or 'weightier' training trips.
Ion: only overnighters so far, but I want to get more out of this one
REI Jet UL: I use this one mostly for soccer gear at this point, but it could fill a niche between my Jam and Ion if I went with a lower volume sleeping pad at 3-4 nights out, I guess.
TNF Terra 30: This was an early acquisition that's prettymuch just a loaner now.
Jansport Carson: Massive external frame I keep around in case one of my friends ever invites me hunting.
Vaude steeprock 30+8: I got this one super cheap, and my little sister is the only person to have used it so far (except for my family's cat, which urinated on it and a few others stacked in my closet)
2 Pinnacles: I haven't used either yet, but one is a loaner and the other may get sold or donated.
Also, I just got a ULA CDT from Will, and it's in the mail. I wonder how many of these it will render obsolete for me.
Oh, and an flash 18 I've been meaning to sell since I got the Ion. I should do that.
I also have a few laptop bags that I got for cheap, used for awhile, and eventually replaced/upgraded/just wanted something new. I did some rough accounting awhile back and realized that, excepting cooking and clothes, I could equip about 5 people to hike at the same time with just my redundant gear (provided they were about my size).
Thanks pyeyo, now I feel melancholy at my excess.