Not just one thing, but various ideas from minds more creative than mine.
SEH
Jump on a grenade without body armor. (This one has been pretty much a given for The Medal).
Wounded, refused evac, covered withdrawal of platoon with last breaths.
Multiply-wounded, and stayed fighting with troops for hours.
Charged enemy pillbox solo with a molotov cocktail and a gauss rifle with 23 rounds.
[Flag Officer] When faced with inevitable crushing defeat, felt really bad about abandoning command to their fate, while making pithy resolutions of return.
Rick Rescorla on 9/11/01.
MCG
Wounded, but waited until all other platoon members were on transport for getting .
Stayed in position for 8 hours while under withering fire that caused some casualties.
Volunteered for forlorn hope mission, and comported self well in the face of enemy fire.
[Field Grade Officer] Flew over battlefield in grav tank and kept a stiff upper lip, while saying very encouraging things over the radio to the poor sods rotting in the trenches.
2LT Rick Rescorla on 11/15/65.
MCUF
Comported self well in the face of enemy fire.
After being ambushed, crawled back into kill zone in a ditch to destroy the crypto, while not knowing if the ambushers were sill present. Returned to unit, and directed entire battalion of tube artillery onto ambushers.
Flew medevac into hot PZ with effective anti-vehicular fire.
Led squad on combat patrol, accomplishing mission and evacuating the wounded in good order.
[Company Grade Officer] Failed to embarass self at the distant sound of gunfire. Made bad jokes in lame attempt at propping up morale.