One thing I will never forget as a DM was the 'Microwaved Dragon'. Played a 1st edition game back in High School set in a home-brewed world based mostly on Mystara. Was bad enough the Fighter found 'Dragon Taming' as a Skill in the OLD Player's Handbook, and even worse when she decided to 'tame' every dragon they came across instead of battling it.
So eventually they became the Dragon Riders, having as many dragons as PCs, and one of the PCs even decided to have a shape-shifting dragon character. At one the group found themselves in the lair of a Medusa. There was an open, central courtyard full of broken marble statues that were the many past adventurers that had attenpted to slay her. The Fighter summons the dragons, who sat perched along the upper rim of the courtyard's roof. Now mind you these are all young dragons, none of them being more than 30' long at most.
In the center of the courtyard is a fountain, with a thin layer of smelly, scummy water in the bottom of it. The shade-shifted dragon walks over to the fountain, and his player declairs "I am going to do something very stupid." Audible groans from the rest of the players as I prepare my dice behind my screen. Sure enough, he sticks his finger in the water, and is imediatly sucked under by a Water Weird. Well, all the other dragons imediatly unleash thier breath weapons. He is burned, dehydrated, frozen, and electricuted. The Water Wierd is destroyed, as was the fountain and half the courtyard, but somehow, he had 1 hp left! From then on, the chracter earned the nick-name of the Microwaved Dragon by the rest of the players.