Instructions
Open "Team Fortress 2."
Click on the "Options" menu.
Click on "Keyboard."
Click on "Advanced."
Click the box next to "Enable Developer Console." This allows you access the developer console interface to enter cheat codes.
Press the "~" or "tilde" button to open the developer console interface. You can usually find the tilde button on the upper-left area of a keyboard.
Enter "sv_cheats 1" in the command line and press Enter to enable cheats.
Press the tilde button, enter "r_drawviewmodel 0" in the command line and press Enter to hide the weapon.