Best Dragon Fight Ever
The party - a fighter, a ranger, a drow rogue, a wizard, and a druid with no animal companion - is coming up from the underdark, and is in a deep chasm in the middle of a forest, during a thunderstorm. This grotto is about 100 ft. deep and 70 ft. wide, with side passages, pitfalls, and a waterfall.
They're trying to find a way to climb up the rainslick cliffs to reach the surface when a guardian of the underdark - a slightly modified green dragon - appears and says that it will destroy them before it lets a drow reach the surface. The party is low on ranged attack options, but thankfully this is 2e where dragons could only use their breath weapons three times a day.
The party starts by scattering so they can't all be hit by the breath weapon. The mage and ranger head in one direction, trying to get to higher ground to find a path to the surface, while the fighter and druid run out in the open, wanting to make themselves tempting targets so the rest of the party can get away. The drow rogue ducks into a narrow side tunnel where the dragon can't follow, and manages to hide.
Irritated, the dragon swoops in and grapples the druid, carrying her off, which ruins everyone's plans. The dragon carries her to a high ledge and keeps her grappled, threatening to kill her if the rest of the group don't turn over the drow. The party refuses, retaliating with a fireball and the ranger and fighter climbing up to try to engage the dragon in melee.
The dragon begins tearing at the druid so it can follow through with its threat, but then the two warriors are nearly on it, so it lets the mangled druid go (she's only a few hp away from death, so she just lies where she is), and tries to knock the PCs off the ledge they're climbing with its attacks. It misses the heavily-armored fighter, and the ranger is an amazingly good climber, and even after getting hit he manages to hold on.
The warriors reach the dragon and start fighting, but the dragon is really just too strong for them. The ranger gets so hurt that he grabs the druid and carries her to safety, while the fighter stands and takes the punishment. The wizard is still on the floor of the grotto, failing against spell resistance (magic resistance back then), and things are looking bleak when the rogue comes out from hiding and calls the dragon out.
The dragon abandons its fight with the fighter and swoops down at the rogue, who at the last minute dives into a pit on the floor (intended as a hazard in the battle, but ending up as a nice hiding place). The dragon exhales its gaseous energy breath attack into the pit, but the rogue reminds me they're in a thunderstorm, so the bottom of the pit should be filled with water, which means the deadly vapors can't reach her. The dragon tries to stick its head into the pit and bite, but the rogue is doing everything she can to stay out of harm's way and out of reach, and the dragon just can't hit.
This daring ploy by the drow rogue gives the druid enough time to heal up the warriors and buff them, and they make their way back down the slope to take the battle back to the dragon. The wizard tries to trap the dragon with a web, which holds it just long enough for the warriors to get in one round of attacks before the dragon decides to screw melee. It takes to the air, swooping past the wizard and knocking him unconscious with one bite, and then flies up to the top of the grotto, where it uproots a tree.
The fighter, ranger, and rogue are at this point looking for rocks they can hurl because they have no ranged weapons, when the dragon throws a tree at them. This knocks out the fighter, and leaves the rogue pinned under the tree. Thinking he has no options left, the ranger waits for the dragon to swoop in for the killing blow, then jumps onto its face, clinging to the monster. It flies all around the room trying to shake him off, wanting him to fall to his death, but the ranger manages to hold on, and even digs his sword into the beasts's eye.
And the druid, who by this point has cast call lightning, brings down two bolts of lightning upon the dragon, killing it.