• Options (Gear icon at the bottom)
  
• Click Advanced
  
• Checkbox for Developer Console
  
• Click Ok twice
  
• Press ` [below esc, above tab]

Once you have your developer console open, you'll want to type the following commands:

• tf_taunt_first_person 1 [The only required one, but the other two will help improve the experience]
  
• cl_first_person_uses_world_model 1 [Actually lets you see the animations]
  
• cl_drawhud 0 [Disables the hud for a better viewing experience]

When you want to re-disable/enable these settings, set the first two to 0, and the last one to 1.

That's all you have to do, and the rest of the guide will be a showcase of some interesting animations.

Enjoy your funny animations, share the guide to your friends if you all want to eat your first person Sandviches and whatnot.
Maybe a funny YouTuber will do it for views, and credit this.