PMV: MLP x TF2 / Legend of the Wonderbolts / I've Got a Theory
The TF2 thing is another "series" possibility. If a few more pop up I'll spin it off into it's own thread like Luna the Lonely Astronaut.
Also another awesome movie trailer, and some Buffy the Vampire Slayer musical stuff.
1.)My Little Fortress - Friendship is Sapping Sentries EP01: Spy steals Soldiers intelligence
2.) Legend of the Wonderbolts
3.) I've Got a Theory