This command only works if you are a server operator! (Being in the main menu, as well as maps loaded offline will make you server operator by default.) meaning that this will not work in Valve Casual, as well as any Community servers not owned by you.

make sure that you have enabled the developer console. This can be found in the keyboard tab of the settings menu. By default, the developer console key will be the " ~ " key.

(step by step guide on how to enable this provided below. click for full size.)

Press the " ~ " key to open developer console. in the console, type in the following command, then press ENTER to run the command.

Once you have finished step 2, you are free to do whatever you'd like with Halloween mode now enabled. You can load any map and it will have Halloween mode enabled, allowing you to wear restricted cosmetics as well as see cosmetic and weapon spells. You can also just open the loadout menu, and see any cosmetic spells you have, great for taking screenshots of things you have.

(I don't own any pumpkin bombs weapons, but they work as well.)

The command tf_forced_holiday has several values. Here are a few other ones that can be fun to try out.

1 = TFBirthday. This makes gib kills spawn confetti, as well as allows the TF Birthday noise maker to work.

11 = April Fools. Taunts have a chance to be replaced with the Schadenfreude taunt! (Laugh taunt)

If you want this command to run as soon as the game launches, you can put it in a autoexec, and it will work!