Sword in the stone

This is one of those classic bits of story/ prophecy that would not survive contact with your average D&D party.

Your PCs would hear of the sword – fated to only be wielded by the one true king –  spend all of 12-seconds trying to pull the sword out normally (just long enough for a couple strength checks), before moving onto Taking 20 on the checks with buff spells to really maximize their pulling power. If that didn’t work then then they’d start thinking outside the box and begin trying to grease the sword or disintegrate the stone.

Really, if you were able to ram a sword into the stone in the first place, it can’t be that dense of rock.