Maybe you could adapt sticks and stones from black ops, where you get a explosive crossbow, a throwing knife, and a ballistic knife. But maybe you can make a ballistic knife by using a pistol with a tactical knife that shoots throwing knifes. But the throwing knifes would have to go further when using the "ballistic knife" than they would by just throwing them. For the crossbow you can use what DEREKTROTTER did ( a 50 Cal. that shoots explosive bullets.) And for the throwing knife you can use the throwing knife
Another idea: A game kind of like a shark and a fish. You can give players jet packs, but they fly up and float down slower, to make it seem more like water. There would be a shark(s) and some fish. The fish can swim faster than the sharks, but the sharks can get a speed boost that builds up over time, that makes them swim faster. If the shark catches up to a fish and knifes the fish, then the shark will get a power up. The power ups can be:
Make fish slower for 3 seconds
Give the shark a wall hack so he can see red squares around the fish (sort of how sharks can smell blood from far away)
Make fish blind for 5 seconds
And for every minute the fish survive, they can get power ups such as:
A speed boost
Invisibility for 5 seconds
Turn into a turtle for 10 seconds (put a riot shield on their back so the shark can't knife them from behind)
And to make it seem more like water, you can add some lighting effects and what not.