- The final challenge
Here you should dish out your best weapons to kill helis as quick as possible because the more time the helis are on the screen, the more bullets and rockets they fire and that makes a quick death and a lower score. This round is "endless"; there is no way to complete it except to die.
Use TimeDistort when the attack heli starts its roundhouse barrage- its machinegun spinning around itself making circles and firing very fast for 5 seconds (as fast as a chaingun you have) - and when the machinegun of the heli is about aim near you (like 30 degrees) use timedistort, this will slow you down also the heli and the bullets, but not the spinning speed of the machinegun (also the firing speed of the machinegun) and the time this ability lasts. So you will have a better chance at dodging the incoming bullets, and the heli will fire only 1 bullet instead of each 5. This will make it much easier to not get hit from that. Also you can still fire your weapons even though its slower, actually this will help you aim even better so you can do it much better.
As an alternative, you can use timebreak too, since it stops everything except you, you can pass through bullets without getting hit. The only downside of that power is that it is consumed very fast.
Upon defeating a heli, sometimes a health power-up drops. If you pick that up, you get +5 health. Initially you have 20 health. Each time you get hit by an enemy bullet, it will lower by 1. Each bomb will lower it by 2, and the rockets will drop your health by 3 (luckily you can easily avoid rockets by running below the flying course of the first rocket or Hyper jumping over the nose of the heli).
Good luck!