Bennies in Savage Worlds, without a doubt. Players typically start with three bennies, which they can spend to re-roll checks and soak damage. Having three bennies at any given time means that players are comfortable with spending them and still having a reserve.
I don’t have a problem with people hoarding bennies because I’m liberal in giving them out. Players know if they spend a benny, they’ll have an excellent chance of earning them back through good role-playing, inspiring actions, funny jokes, etc. This sets up a virtuous loops where people are willing to take risks because they know that they have a better than normal chance to succeed … and even if they fail, that failure might earn them a benny to replace the one they lost.
I also use inspiration in Dungeons & Dragons 5th Edition, but I find that it’s not as useful. People like having inspiration, but they tend not to use it except in desperate situations because they only have one of them. I still reward them liberally, but the same sort of positive feedback loop is rarely set up in D&D.
Perhaps my favorite game mechanic is Fate points in Fate-powered games like Spirit of the Century. They’re similar to bennies and inspiration, but I like them better because they evoke aspects of your character.
You can spend fate points to invoke an aspect, to declare a story detail, or to activate certain powerful stunts.
You earn fate points by accepting a compel on one of your aspects.
A word of warning: don’t use edible things as tokens, especially if the food hasn’t arrived yet.
— “Fate Points” from the Fate SRD wiki entry
What’s great about Fate points is that — as the game master — I can tempt players into using one of their negative aspects (aka a flaw) at the table. This helps with the character who chose an aspect like “Hot-tempered” or “Can’t say no to a fight” but then never uses it when the situation calls for it because the player’s metagaming and knows it wouldn’t be in the character’s best interest. Fate points short circuit that logic by providing a clear benefit to evoking a negative trait. It can make for some exceptional games as players are motivated to bring all aspects of their characters to bear … and not just the ones that are obviously useful.