Personally, I like a little more room to move.

With this in your M1 folder, you can drop any map (in that folder) on it, regardless of name, and double-clicking on your Marathon app starts a game using that map. Want to use a different app? Drop it on Map Select, and it will be the one modified with new map names. Brings some of the convenience of M2 to M1...

"Alien" the movie, feel.

Lets you edit (and create) physics models for Marathon.

Lets you move different levels between Map files. You can make a Map file with only Waldo World Arena in it to bring to net games, for example. (Warning: this program is incompatible with maps made with the latest versions of Pfhorte, and the author has no plans to update it.)

Creates a "patcher" that contains only your changed shapes. Don't distribute huge Shapes files! Use Shape Shuttle and save up/download time!

Textures that feel like star trek the next generation.

Provides very primitive tools for converting Doom WADs to Marathon maps... in a many-step, tedious process.