+1 on the Benadryl. I carry it with me everywhere I go. You never know when you (or someone you're with) might have a weird allergic reaction to something.

I also carry an "emergency card" in my seat bag which has photocopies of my driver's license and insurance card, other medical info, and emergency contact info. I had a line on my RoadID engraved with "emer info in seat bag" since it's kind of hard to fit all your important info on the RoadID itself.

Otherwise I pretty much carry the same thing everyone else has listed.