Decent street maps are normally the first thing I buy. I've gotten turned around too many time relying on the rent-a-car maps.

The bottle of any prescription meds along with the more common travel stuff (dramamine, tylenol, antacids).

A flashlight (keyring for the city, pen light if I'm going out a ways).

Compass (it can take a couple of days for my sense of direction to kick in).

Water bottle(s) (fill it up after getting through airport security)

Still working on a way to deal with cutting needs for carry-on only travel. TSA has proved extremely capricious as of late (e.g. cut the TSA approved locks off of the suitcases going in both directions), and I'm not sure I want to risk a decent pair of 'approved' scissors or a Gerber EAB sans blade. Maybe I should just buy a cheapo utility knife when I get there.

It sounds like I should add a sewing kit, FAK, iodine tablets, and the locations of any potential disaster relief facilities (red cross, schools, stadiums, etc.) to my bag.