I was torn on how to answer this as the last game I played and the last game I ran are two completely different games and systems. So I thought I'd touch on both.
The last game I played as a player would be in Jim Yoder's fun-filled DCC RPG game back in May. (Has it been that long? Yipe.) Jim ran a few of us through "Mall Maul", a 0-level funnel from the Crawling Under a Broken Moon zine, a DCC zine focusing on post-apocalyptic adventuring. Our happy band of bikers, scientists, and burro herders (seriously) explored the rundown abandoned shopping center with much laughter and good-natured gonzo fun. Many deaths due to lasers and mutants were had that session. Great fun, and I look forward to future DCC madness in front of Jim's Judge's Screen.