For DLC items, I have a cat tower and a shaved ice lamp. For unorderable stuff like from events, I have the picnic basket, Gulliver items, HHA awards, trophies, etc. It really depends on what you want specifically. ^_^
I've got all the Best Buy DLCs and the reorderables like Aurora Screen and Campus set. I guess looking for Japan/Korea exclusives like 7-11 and their Holiday items.