Now, for stories from actual games I've run:
Back in 2nd edition when I was a new DM with young and inexperienced players: They are searching a cursed temple. The first trip they lose two people to a gargoyle golem(when it hits it petrifies, hits again to shatter) and it chases them outside. After getting their friends rez'd, they head back, playing hit and run with the golem in the woods. The wizard decides to levitate it so he can force it to the ground, then lassos it and ties the rope to his waist of all things. The golem looks at him, looks at the rope, then takes off dragging the mage off through the bramble filled woods.
Also in the temple they find a library full of dark tomes and a glowing pentagram on the floor.
One of them touches a bookshelf. *BOOM* fire trap. Not deterred, another player winces and touches another one. Nothing. So he grabs a book off the shelf. *BOOM* fire trap. Still not deterred, another player winces and touches a bookshelf. Nothing. Wince, pulls a book of the shelf. Nothing. Opens the book. *BOOM* firetrap.
I figure they're deterred by now, but no. Yet another player does the same routine: wince/touch/wince/pull/wince/open. The player grins. "Clear." Starts flipping through the pages, finds it's warping his brain, so slams it. *BOOM* fire trap.
Fed up with the books, on of them shows his distain by throwing one of them into the pentagram on the floor, the ritual on the pages triggering the pentagram and openning a portal to the hells... They only survive by running like hell as the uber-wizard of the world drops a meteor on the church to seal the portal.
---
Later in the game, the wizard(the player of the wizard went through 13 characters in the span of the game) was experimenting with Transmute Liquid, trying to find "the most explosive liquid there is." He of course tested this by scooping water into a bowl and then lighting it on fire. He did this every time the PCs made camp. They knew he found it when he went flying over the camp training flames.
Once they'd put him out and healed him up, they decided to use a barrel full of the stuff to destroy an army of goblins that lived below a nearby tower. After planting the barrel with a long fuse, they riled up the goblins, mounted, and waited for the goblins to come pouring out. The grand plan was that the wizard with through a Flame Disc to light the fuse as they rode off. Unfortunately, he missed and hit the barrel instead.
They wizard died instantly, while the Paladin woke up on his mount... in a tree, 200' from a huge crater.
Fortunately(un-fortunately?) the wizard's spell book survived and the party's new wizard decided that they'd try the whole deal on a larger scale. They went to town, got a water wagon, filled it with water, made a 1000' long fuse, then transmuted the stuff to the super-ultra-mega explosive. They then halled it to ye old Necromancer's Castle and parked it just outside the gate. As the undead began to swarm, they stood about 50' from the water wagon and discussed when/how to light it. At about that time, the Chaotic Neutral dwarf lights it, interrupts the discussion, taps them on the shoulder, and points.
Miraculously, all survived except the wizard whose levitating body was found skipping across the ground at 40mph.