In 5e D&D fighter's have a subtype that get these cool sounding things called maneuver dice. They're actually d8s that let fighters do stunts. Unfortunately they are little more than vehicles for bonus damage in that system. So in OSR fashion I thought I would see what other places I could take maneuver dice and make them a little more interesting.
First of all, they're called stunt die. Maneuver is a laborious word and it sounds boring after the umpteenth uttering. Stunt is way simpler and rolls of the tongue like a machine gun. (stunt! stunt! stunt! stunt!).
Next every class has a single stunt die. This should probably be a d8 for fighty classes (i.e fighters), a d6 for not-so-fighty-but-still-fighty classes (i.e. specialists, clerics), and a d4 for not-remotely-fighty classes (i.e wizards).
The maneuver die can be used when attempting stunts. You roll the die alongside your attack and if you hit and the stunt die meets or beats a TN, determined by your referee, your stunt happens! Don't worry if you miss because if you do your stunt die goes up a level (i.e d8>d10>d12> ...). It also goes up a level if you land a crit or someone fumbles against you. but beware! Your stunt die levels down if you fumble, are hit by a crit or a stunt.
The increasing-decreasing levels encourages sides to compete for the upper hand. Eventually PCs and monsters alike will be flying around kicking like they're in an Ang Lee film just so the other side doesn't style on them.
Here's an example of the mechanic in action. Fangrot the Fighter really hates the look in that orc's eyes, so he decides he wants to pluck one out with his trusty dagger. He tells the ref. The ref thinks gouging someone's eye out should be fairly difficult so he assigns a TN of 6. Luckily Fangrot has been pretty showboaty this combat and has leveled his stunt die up to a d10. He rolls his attack...and hits! He rolls his maneuver die...and it's a 7! Fangrot holds the orcs eye in between his thumb and forefinger as he mocks the creature's painful screams.
For those refs concerned about which TN is suitable for which stunt, most of the time 4 is acceptable for simple actions. These are usually the "I want to disarm X" or "I attempt to shatter his shield" type actions. Add 1 or 2 to the TN for each factor you think makes it harder (i.e. X is wearing a weapon chain or the shield is adamantium). If you want to be cheeky make it harder every time your players say "and" because usually stunts with "and" thrown into the mix are more complex and therefore more difficult.
You could also tack on bonuses to the stunts die's result, be it bonus damage or dismemberment.