I'm curious because I just spent most of the morning creating some fake paperwork in a beat-up manila folder for the next game I am running. A new NPC is going to give one of the PCs a folder full of information they may want, and when that happens I will hand the player the actual folder I made with that information in it.
I've also made a distressed map for the players to follow for a one-shot. Any miniature-heavy game is sure to have me making custom miniatures for at least me, and usually the whole group. We also have several toy lightsabers for enacting lightsaber battles. There is also a set of Halloween kitty ears floating around here somewhere from when I played a Catgirl.
Good, bad, or neutral, what are your opinions on props?