What do you regret NOT buying?

I regret not having Gymnastics Lisa -- i wasn't playing yet when she was first offered and I'd love to have her. Only regret so far, not getting the Christmas thang that lets Homey fly over Springfield in his sleigh. I've learned my lesson: made sure I got everything in the yard sale, espec. Mayan team. I missed the first Whacking Day by mere days, and I was glad to have Ninja Homer, but I would like the chance to buy more whacking stuff, or even better, whack away!