OK, ideas then - I don't have to worry, my entry is complete, so I wouldn't be using any of these, but here goes...

1. Create a linear dungeon map, have the PCs chase a wounded BBEG that lost the encounter with the PCs and is trying to escape to fight them in the future, but somehow botched his escape plan so he's working on plan B, which is to get to some teleportation chamber on foot. If the PCs can catch him, they can end his chance to ever come back. Create a dungeon map from point A to point B.

2. Zombie invasion - some eldritch device which is causing the zombification can be shut off to end it altogether. The PCs need to get to that device and shut it off, which may cause all the zombies to fall down dead when this happens, meanwhile a multitude of zombies are trying to eat the players to prevent their demise. This could be a street map, make it linear it works.

3. PCs are escaped prisoners from a prison camp behind enemy lines. The underground has a safehouse located in a hidden forest location near the front lines. The PCs have to negotiate their way around military patrols, a fence or wall that contains the area behind enemy lines. The PCs must try to get there and not be caught by SS patrols, road blocks, etc.

4. The PCs are reporters trying to discover the true identity and secret hideout for their local superhero (superman, batman, the Tick, whatever).

5. The PCs are aboard a starship. There captain and senior crew have been captured by the Xenomorphs who've attached their ship to the PCs ship hull. A secondary bridge must be accessed to take control of the ship back, and arrange the release of the senior crew. However, main corridors are blocked so the PCs must crawl through ventilation system and maintenance corridors to reach the secondary bridge, meanwhile Xenomorph hunters are behind the PCs trying to stop them.

I could come up with a dozen more, but this should be enough of a start to generate your own ideas.

Let's see some competition here!

GP