I dont usually even look at these, but I came a across a few of these today:

Gundam 00 Danjo:
http://www.youtube.com/watch?v=KhWfE...eature=related

Gundam 00 x Code Geass:
http://www.youtube.com/watch?v=-5ei1...eature=related

Gundam SEED Destiny ED X Gundam 00 Kimi wa boku ni niteiru:
http://www.youtube.com/watch?v=WOW-S...eature=related
(this one in particular had a lolwut? ending)