The Junkyard 1.2
A ten-level solo scenario, and a net level (Lava Extreme, also available separately) Some of the levels are bigger than others, but except for the last one, you can run through the whole thing in under an hour. The story revolves around Durandal and Tycho, but they're not the Durandal and Tycho you know... Use IZD on an 040. (The last level shows what happens when you give someone All Roads Lead to Sol and DOPE and tell them, "make a level kind of like this one, but with more monsters.")
Levels in map "The Junkyard 1.2":
Water Refinery
Weapons Galore!
Have Goop, Will Travel
The Sewer
Man, those birds are noisy!
Weapons + Ammo pickup
Save the Bobs!
You big Worm!
The Pop-Can
Grand Finale!
Lava Extreme!