The Binding of Isaac: Rebirth

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You can get this on every run. You just have to get to mom within 20 minutes. It's pretty cool and gives you motivation to go fast.

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AH! I see. I've been wondering what happened if you managed to reach the boss before the clock does. I'll be keeping it in mind for future runs :3

Have you guys tried any of the challenges yet?
The "High Brow" challenge is a lot of fun, it gives you various ways to turn enemies into poop, and starts you off with an item that makes nearly all poops give money and keys and such
and "The Tank" run was amazingly fun, starting you with 7 hearts, damage reduction and letting you break stuff by stepping on them.
"Computer Savvy" was... insane. Technology 1 + 2 and homing shots. You could wipe out an entire room of enemies with chain lightning, crazy.

Meanwhile "Head Trauma" is annoyingly difficult.