GURPS, the Generic Universal Roleplaying System, uses only d6, with the biggest rolls tending to max out around 10d6. It's very flexible, and is based around the power scale of "heroic realism", aka action movie schlock. Characters can do badass stuff but if you get shot you typically die pretty quick. I've used it to run/play in the following games:

• cyberpunk heists
• kung fu movie knockoff
• D&D with the serial numbers filed off
• tactical mech combat
• rules-light game in not!Ancient Greece where the PCs were godlings
• post-apocalyptic road trip
• galactic merchants
• rowdy teens vs sasquatch
• the movie Alien
• Delta Green with the serial numbers filed off