I live in a
very rural area, but occasionally visit "the big city"

I started a similar thread some time back and the points that stuck home for me were:
suitable clothing for the season (this doesn't change rural or urban), blend in - neo-tatical is not the route I'd choose for traveling afoot (or bike) in the city;
water- priority regardless of environ- water tabs are small and effective, some kind of container- you can roll up a platy bottle into a very small package until needed;
fire- very important in a rural environ, less important in a city- I'd still want a couple of small lighters and a little easy tinder- less than an ounce total;
shelter- a AMK heat sheet takes up about as much room as a deck of cards, add a 2-3 mil large trash bag for additional insurance, small hank of paracord;
protective bits- eyewear, good gloves- these are carried rural or urban- for city I'd add a couple of quality masks;
tools good multi tool at a minimum- don't use one much personally, but would be very handy in the city-small fixed blade/folder depending on laws;
communication- a cell phone you might as throw out where I live, not so in the city, a little fm/weather band radio could prove very handy in the city;
first aid- compact and well thought out;
$ several denominations;
navigation- some good maps and the ability to use them, small compass- even in the city it might come in handy;
lighting- a quality light/headlamp, w/ a small backup,
signaling- quality whistle;
food- not a lot, but a few calorie dense choices;
repair-small kit w/ extra batteries for your electronics- this might be a place where you can try and replicate battery type
a suitable pack/bag- again something that blends in