Valve Launch Source Filmmaker Open Beta
This software is available to all Steam users, and will allow you to make your very own animated videos using assets from games like Team Fortress 2 alongside a large amount of camera tools as well as editing, animation and lighting tools.
You get more than just TF2 with the beta. There’s all the assets for two of the “Meet The” shorts, allowing you to use pre-existing footage as a playground to practice your skills. There’s some tutorial videos which can help teach you all about just how you can use the software as well.
I know this is probably one of my favourites: