Re-obtain deleted weapons in Garry's Mod?

If you added it from the workshop:

• Go to Garry's Mod Workshop
• Find it in the Workshop
• Unsubsribe
• Subscribe again

If you added it yourself:

• Make sure it is deleted from Garry's Mod files completely
• Close Garry's Mod
• Put the file(s) back where they belong

If it is part of Garry's Mod default

Option 1

• Make sure it is still part of Garry's Mod and that it has not been removed

Option 2

Note: This may take a while depending on how much you have used the game

• Go to your steam Library
• Right click Garry's Mod
• Click Properties
• Click Local files
• Click Verify integrity of game cache...

Option 3

Note: This is a last resort

• Right click Garry's Mod
• Click Properties
• Click Local files
• Click Delete local game content
• Wait for it to finish deleting
• Download the game again