I recently got to take a break from running my own ACKs game to try out a game soneone else was running. We'd previously worked with Blades and Black Magic, an a game inspired by TFT by Steve Jackson Games, but deecided, for an additional change of pace, to go with something more narrative that didn't end up taking hours just to resolve a combat or two.
Thus, Dungeon World. The SRD is here, and prefab character sheets are here.
it's a 2D6 based fantasy RPG with 3D6 stats, and a much fuzzier roll resolution system. Generally, anything under a 7 fails, anything over a 10 is a straight up success, and anything in between is somewhat of a success, but things didn't go as well as planned. perhaps you got injured, tripped, etc.
The system itself is pretty simple. There is a stock repertoire of "moves" every character knows such as "hack and slash" - a basic attack attempt - "parley", "take watch", etc. Each class also has moves specific to itself such as the Paladin's "I am the law" command somene to do something, or stop, because you are a paladin) or "Backstab".
There are no rolls for initiative, everything is played out narratively. And you very much can get killed if you are not careful. Leveling up doesn't get you more hit points, but it does allow you to select a new type of move - similar to what 3.5/Pathfinder would call a feat - every time you gain a level.
Of interest - to encourage people to jump in and take chances and make decisions, you get XP when a roll fails. Also of interest, there are relatively simple but well-defined conditions for gaining XP that in other systems would be awarded for vague things like "good role playing".
Because of the very light ruleset, prefab character sets, and narrative play style, it is excellent for pick-up games and scratching that RPG itch when time is limited. It also doesn't lend as much temptation to the crowd that wants to write up a threee-page backstory for their characters.
Since the SRD is freely available along with the excellent play kits, give it a shot.