If you put two gravity volumes inside of each other, everything inside will levitate.
Actually, I made a gametype out of this, similar to that 'Trash Compactor' infection gametype in Halo 3. One person spawns outside the gravity well (which is fairly high and contained in a series of walls) and throws sticky grenades in at the other players, who have to try and dodge them. Since grenades don't prime unless they hit the ground or stick to a vehicle/person, they will float endlessly in the air.
It's actually a pretty hectic and amazing gametype. I recommend trying it out some time.
Also, this gravity thing is pretty fun for creating maps in Impact, where you can just have objects float endlessly. --- People really need to stop complaining about the inclusion of online passes...
You can shoot the Sticky Detonator explosive, whether it's already planted or in the air. If you time it perfectly you can kill someone who's wielding one with hilarious results. Or, if there's one planted on the wall/ground blocking you, just blast it. --- Ab-so-lutely.
When you pull out the Hardlight Shield, you can direct your facing before it is all the way out (so If you hold right while pulling the trigger, you'll spin and face that direction)
Similar to the Banshee loop. If you're holding right when you're doing it, you'll turn right when you come out (essentially, the game keep track of how long you held right, and you'll start to turn that direction as soon as your loop ends. YOU CAN CONTROL YOUR FACING COMING OUT OF THE LOOP!)