Apocalypse World introduced the concept of clocks to tabletop gaming. They’re basically a countdown timer; you increment the clock by a bit every time someone gets closer to a goal. They’re also used as health bars. Not insanely novel but it’s useful to have a visual representation of impending doom or success, as the case may be.
In my Bookhounds of London game this weekend, I ad hoc used a six sided die as a clock. I hadn’t been planning on it, but a chase scene arose spontaneously and the 13th Age escalation die came to mind, so I plopped down a six-sider with 1 showing. Then I said “OK, the one goon just vanished around the corner while the other goon stands to hold the hallway against you,” and flipped the die to 2. My players needed no other explanation.
So that’s a cool trick.