PermaProps allows you to save entities across map changes. There may be other version of this script, but this addon makes it as simple as point and shoot with a toolgun!

Basically, you spawn an entity, and then permify it by using the PermaProps tool, and shazam! It's done. When you go back to that map again, you can find that prop in the exact same spot with the same color, model, and everything!

You can save not only props but almost any entity, including SENTs, ragdolls, SWEPs, and more!

Stay tuned, because more features are planned and will be implemented as soon as possible.

Thread: http://www.facepunch.com/showthread.php?t=960173

SVN: http://entoros.googlecode.com/svn/trunk/gmod/permaprops
USE THE SVN! I'll put bug fixes, new updates, and more on there.

Note: There will probably be bugs, as I don't have a huge office of fieldtesters to back me up. Please tell me if something's wrong, preferably in the FP thread.

INSTALL DIRECTIONS:
Place it in your addons directory.
garrysmod/garrysmod/addons