My father, who taught me the joys of RPGs, was a First Edition Dungeons and Dragons player back in the '70s. His gamemaster was a bit bloodthirsty and liked to roll everything. This is his story, and all the background you really need.
My dad's party, which was composed of a rogue (my dad), a mage and some three or four other people (the information isn't really relevant) came across an old, beat-up wand at the end of a campaign. Being moderately intelligent, the mage took it into a town and had it appraised. Lo and behold, it's a Wand of Summoning! And what does it summon? "Whatever you darn well want," replied the gamemaster as the old trader.
So they take it with them into the next dungeon and promptly get themselves trapped in a room with no less than 70 kobolds. Not particularly powerful things, but there are 70 of them and about five PCs. They need help. So what does the mage do? He draws the wand and yells, "I need warriors!"
The gamemaster decides that an exorbitant number of dice rolls are necessary to determine what shows up since the mage, forgetting the words of the traveler, didn't really specify what he wanted. Two or three minutes later, the gamemaster announces that there immediately appears "a dozen SS (German Secret Service) soldiers from 1945, armed with a Luger, a submachine gun, and 6 hand grenades each!"
The sad thing is that the whole thing might have worked if the SS soldiers had made their morale checks. As it stood, the last thing anybody in the room (SS, kobolds, PCs, everybody) ever heard was no less than 30 hand grenades going off, gunfire, and swearing in 20th century German.
Moral of the Story: Be careful wand you wish for--you just might get it.