...the security tag I use to let myself in at work.
And my antidepressants.
I'm more worried about the latter (although as they were running low and I was thinking I need to get a new lot anyway, that's not the end of the world; but I may be a couple of days without them, which is never a terribly good idea - the main reason I can tell they're working is that I feel substantially crap a day or two after not taking them at my regular time...)