I'll admit, I have an obsession with companion pets -- much to my warlock's chagrin. She'd much prefer to burn the little critters, but I can't help amassing as large a collection as I can. At last count, I had over 100 pets and am still striving to get even more. While I have several titles, special mounts, and the like, I devote more time to building my pet collection than anything else.
Of course, my collection wouldn't be where it is today without the help of some really good friends (especially the one who tirelessly slaved away killing Bogflare Needlers for my coveted Captured Firefly -- eeeek!).
Do you collect anything in WoW? Whether it be common things like mounts or titles, or something a little more obscure, I want to hear about it -- unless, of course, you have a better pet collection than I do. Don't make me cry.