I had an idea for a leveling system that might work in an action movie/martial arts kind of game. Basically, when you get XP/levels, you can either spend them immediately to learn new abilities, or save them. If you save them, you can decide to have a training flashback at any point, and gain an ability (permanently) at an increased cost.

This happens all the time in movies; the protagonist gets stuck in some tricky situation, then we flashback to a time when he/she learned some skill that deals with that situation perfectly, then we come back to the present and they win. I was specifically thinking of the grave escape scene in Kill Bill pt. 2.