Barbedpilot
Professional Insomniac
I recently discovered this because I was big dumb and didn't know, so I thought I'd share it to help others that didn't know either.
Basically, there's a 64 bit beta version of GMod currently out that everyone has access to, and if you have a 64 bit computer (Basically everyone does now due to FUTURE) then you will be able to use this beta branch and get a nice frame increase
If you don't know how to do this,
Right click on GMod
Click on "Properties"
Click on "Betas"
Click the drop down menu and select "x86-64 Testing 64-bit builds"
Close the menu and update GMod
Note: Applying this beta will have you be required to open GMod directly from steam, and you will have to select the 64 bit version of the game every time. You cannot open it from right clicking steam on the task bar and shortcuts (I think for shortcuts it doesn't work)
Another note: This is a beta build. Use at your own risk.
Basically, there's a 64 bit beta version of GMod currently out that everyone has access to, and if you have a 64 bit computer (Basically everyone does now due to FUTURE) then you will be able to use this beta branch and get a nice frame increase

If you don't know how to do this,
Right click on GMod
Click on "Properties"
Click on "Betas"
Click the drop down menu and select "x86-64 Testing 64-bit builds"
Close the menu and update GMod
Note: Applying this beta will have you be required to open GMod directly from steam, and you will have to select the 64 bit version of the game every time. You cannot open it from right clicking steam on the task bar and shortcuts (I think for shortcuts it doesn't work)
Another note: This is a beta build. Use at your own risk.