Mr. Flipper (opens in new tab) is one of the strangest games I've come across. One of the most left-field ideas, but implemented wonderfully in a cartoon pinball game that seems to have come from the same neighbourhood as Rocko's Modern Life, and Toejam and Earl (ie, the '90s).
In it, you play as a pinball flipper with the singular power to come alive. To run around on an extremely tall pinball table, chasing after a ball that seems determined to fall to its doom. Your enemies include gravity, naturally, but also roaming monsters, and a steadily rising pool of lava that will destroy the ball if it lingers too long inside.
By flipping between the two modes constantly—normal pinball flipper, and a frantic character running after the ball—you're able to slowly ascend the enormous pinball tower, and reach the even trickier geometry of the upper table. Or, rather, you are if you're not me, and actually good at it.
This is one of those agonising games where messing up even once can cause you to lose minutes of progress. So you'll need a tolerance for frustration to see more than a few metres of this wildly inventive, enjoyably strange pinball game. (Via Warp Door (opens in new tab).)
For more great free experiences, check out our roundup of the best free PC games.