Also the grapple hook thing is a life saver, though it can be a bit finicky at times (when you see the quick grapple animation though nothing happens).
it is really good, when i was facing skipper587 i used it to hover over him, took out my plasma gun (a glitch with it though is unless u move, if u change your gun u still float there) and before he could look up to shoot me i killed him
i dont get like the gravity hook. maybe i dont know how to properly use it but when i used it in a practice match, i got last place with 0 kills.
The Antimatter Jet Gun was frustrating to use at first until I realized its not designed for head on warfare, its all about banking the shots around corners/ledges. Got a "sniper" up on a ledge and you cant get a LOS on him..... go right under the ledge and bounce a salvo of AM-Jet shots off the ceiling into his alcove. Know there's someone around the corner....bank a couple of shots into it. The AM-Jet gun gets waaaay better when you upgrade its clip size and damage, so you can saturate a small area with 6+ bouncing balls of pain at a time, best if used as a secondary with a more direct primary gun. I see this gun (when upgraded) being a strong backup weapon for certain people.
You need to upgrade it more to fight people who have upgraded suits and weapons, although none of the weapons are useless at all. Edit: AM-J is great when purchased initially, but if you upgrade it you can kill anyone who charges around corners.
I've been using the plasma cannon since I could buy it, and it's done me great. I've been getting killed by the higher skill levels (I'm at 2100 or so) and I just discovered that aiming ahead of the opponent (Jesus why haven't I been doing this) is a great technique and I'm fragging wayyyy easier.