Schwalbe Marathon Plus, I have the 32c version on one of my bikes and its a badass tire, over 2000km on them and not a single flat so far, and if you can go wider then 28c on your city bike I recommend doing it. I went from riding 25c Gatorhardshell tires pumped to 120psi to the 32c marathons at 70psi and the improvement in comfort was amazing. It did slow me down but it wasn't anything too significant.
Another great option is the Panaracer RIBMO, had the 28c foldable version on another bike of mine and only got one flat when it was extremely worn out.