I know I've read of a way to spend bennies to use an edge on the fly. For example, a player could spend a benny to buy first strike before an opponent moves and then attack them (per first strike's rules). After that round, the edge is lost unless more bennies are spent.
I believe the edge that is purchased has to be a combat edge. I can't remember where I read about this ability, or if it's an edge itself or an alternate rule. I skimmed through the Deluxe edition but didn't see it immediately.
Has anyone heard of this rule before, and know if it can be found in any books?