This is a useless glitch, but may make a funny killcam here or there. You will need a friend on the other team to help you do this
1. In Array, head to the giant tower, the one near bomb A where people snipe off of
2. Have your friend climb the ladder so you can see him in front of you
3. Go behind the ladder and knife your friend
4. You will automatically shoot up in the air
Cannot do additional tests but can someone confirm if this works in WMD or Crisis?