If the lightsaber does not work on your server, Or it just does not work at all, The colisions work, but the damage is negated completely, Then try this:

Disable your addons one by one untill it works, Then re enable all of your other ones, then find a replacement for it,

Check your TICKRATE. If your tickrate is below 66 then it wont work for me. Also, Gmod wont work well with a tickrate of 100.
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Thats what I found. But these still DO not work, So it can't be my addons, I installed on a vanilla server. Any fixes, / workarounds?