Following up on this...

A warrior-type can scream a battle-cry once per combat to get a +1 on an attack roll. The player must literally scream. If screaming is not appropriate right now, you may quietly make a hell of a show of how berserk your PC is going instead.

Rogue-types may pantomime the skill they are attempting and then strike a flashy pose for a +1 on a skill roll. This may be done once per skill per session.

Pictured: 6th-level thief????

AND ANOTHER

This one won't work in my current campaign. Some day though.

Once per session, a character can try to do something totally impossible. They can work a wonder.

A fighter can jump 30 feet in the air and slice of all of a hydra's head. A wizard causes a foe to explode with a glance. A cleric commands the clouds to part and the great face of their god looms above, throwing down thunderbolts. A thief runs down a hallway, setting off and dodging every trap with her eyes closed. Something ridiculous and spectacular and kind of anime.

I don't think this image works that well unless you've seen the episode but oh well.
Roll under level.