Spectre FTW! As I love glitching around, the Spectre is clearly my favorite vehicle. It might be quite bad in real games, but it's boost was so powerful and awesome! Ever tried to boost while braking (L+A)? If not, try it. It's awesome! Very useful to climb angled walls like on Burial Mounds, Coagulation and on top of Containment. Oh, and it looks awesome (the boost trick).
Another Spectre glitch! This one works the best when you park the Spectre on a Wraith (it's hard to explain, but the driver's seat in the Spectre has to be on the cannon of the Wraith). Then you jump on top of the Spectre and stand on the "ledge" between the driver's seat and the plasma cannon. When you're standing still (not shaking), you start crouching repeatedly. Sounds weird, but just keep crouching, uncrouching, crouching etc. Not too fast, not too slow. When you've done this for around 30 seconds or more, you jump. If you do it correctly, the Spectre jumps up quickly, launching you into the ceiling or sometimes death. It's so fun to do!
As you can see, Spectre > all other vehicles (for glitching) ;)