How do you remove everything from the game that you've downloaded?

[Shadowfire2116]

If anyone could help me I would love to know if there is any way that I can remove everything that I have downloaded on Gmod and just start over. I would just go through but there are some files that I just don't know about if they were there to begin with or I downloaded it. And I tried deleting all local content on steam and re downloading it but once re-downloaded it came back still with all of the crap that I don't want.
If there is anyone who can help me with this please do.
Thank you
-Shadowfire2116

[marcround]

delete the local garrysmod folder in steam/steamapps/accountname/garrysmod and then run the game again to make steam extract a fresh copy of the content from the gcf files

(incase you just deleted the gcf files before and not the local account content)