My first draft dungeon (and I'll be changing it as ideas come in until game time tomorrow!) sees the following encounters in the dungeon:
1. three kobolds arguing over dice.
2. a gate trap. Easy to disarm. Spikes deal damage
3. Gas Spore over a treasure chest. If it explodes, most of the nice stuff in the chest (including trinkets, the best treasure!) is destroyed.
4. Pool of green slime. There's a cage over it, with a leather cord that can lower the cage into the pool. There's a dead kobold inside.
5. A weird altar with candles and skulls. Inside the skull is a gem (natch). extinguish the candles and the god of undeath gets angry and you have disadvantage on all saves versus undead attacks for 1 day.
6. 4 kobolds and 2 trained giant rats. The "big fight".
7. A sword in a stone. Pull it from the stone, and it animates and attacks!
8. A cave in. Lots of hints that it's coming.
9. Kobold hiding behind crates. She has a crossbow. She doesn't really want to fight.
10. A ghoul, chained to a wall.
11. 3 kobolds with 2 skeleton pets, guarding a warhorse (the reason the PCs have been sent into the dungeon).
It's a simple, one hour to create dungeon, but there's enough choices that the players should have fun. Any ways to make it awesome(r) are greatly appreciated. Would prefer to keep it simple.