An actual physical key that I have to turn to start the engine. There's something very affirmative about it, and it's been replaced with a rather sterile "brake-push-start" sequence. I realize that behind the scenes it's all the same thing (no flick of the wrist will crank an engine, of course), but I still like the analog aspect of the key. Maybe that makes me a hipster.
My remote chews through the tiny CR2032 battery every couple months, and when that happens, the car (a Mazda, fwiw) no longer detects the key and refuses to start until I bring the key within close proximity of the ignition.
A physical key would sidestep the problem altogether, although I imagine there are HN commenters now ready to reply that a key-ignition car is easier to steal, or something.