Forget about compulsively collecting every useless bauble, or heck, even normal adventuring in Skyrim. That's not worth going back for. This is.
Check out this strange but hilarious mod by rsv_rsv. It gives you the ability to kiss everyone in Skyrim. Well, almost everyone. You can't kiss creatures, mannequins or corpses — which is bullshit, because I wanted to kiss all the mudcrabs. I guess kissing all the Jarls and being rewarded for it will have to do.
(I'm only half-joking. I think I would seriously embark on a quest to kiss everything in Skyrim. Better than, like, collecting all the cabbages if you ask me!)