With this setup, a player would use an Exoquatic Armor, a Antimatter Jet, and any secondary weapon, though I will write the strategy with my choice, the Gravity Hook.
First, I suggest upgrading the armor. I use an armor upgraded with the following:
Shielding upgraded 3X:
This seems fairly small, but my armor is capable of surviving 4-5 blasts from a basic Hellfire Jr., and 1-2 blasts from more upgraded models.
Targeting upgrade 2X:
More damage helps, regardless of the strategy. Combined with my guns upgrades, 1-2 clips can take down a tanker.
Speed upgraded 3X:
This makes me faster than most other armors, and capable of dodging splash from the explosive weapons. It also helps in beating enemies to powerups.
[EDIT] Superscooper7: I've used this strategy and it works. However, do not upgrade your speed that much, or you may run into your own bullets.
Jump upgraded 2X: This allows me to jump the gaps near the berserker shield in Runoff, but I never saw any other need for jumping high with a gravity gun.
Aquatics upgraded 2X:
Being fast underwater means you can escape in levels such as Tank or Runoff.
Second, upgrade the Antimatter Jet. Mine uses the following:
Damage upgrade 2X:
This increases your firepower quite drastically. This, combined with my armor's targeting, means I can quickly take out even tanker prototypes.
Capacity upgraded 2X:
I would upgrade more than this, but it's ok for starters.
Rate of fire upgrade 3X:
This means you have a fairly quick gun, which, when combined with the bouncing bullets, makes it good for both rushing and sniping. I don't suggest cornering with this gun, however.
Zoom: Not upgraded. I'd just turn it off.
Reload upgraded 3X:
Without this, the capacity is too small for close range combat.
As for the Gravity Gun, I'd upgrade the range 3X
With all of the above, I'd upgrade more if possible, thats just what I've done so far.
Snipering rofl: use the Gravity Gun to get high up in the map quickly. If you change your aim and refire in mid-air, you can move quite quickly, and fool anyone who saw your first shot. Then, take an unblocked wall/ceiling and shoot at anyone who comes by. Odds are, they will think you are cloaked or around the corner, as the Antimatter Jet's bullets bounce. Alternatively, you can hide underwater, since you won't drown, and shoot at anyone who passes by. In Lift, you can use the Gravity Gun to move faster down hallways, and reach the Berserker Shield. In a pinch, or if another sniper goes for the place you aimed for, you can use a few shots from the Gravity Gun to take them out, though you will probably get their attention.
Rushing/Charging: This strategy is quite simple. Just run in at close range and shoot whoever it is in the face. Odds are it will surprise them enough to make them hesitate, and your armor can take a few clips, unless they have a Hurricane or Hellfire. Afterwards, run away and repeat. All the better if you have the cloak or health recharge powerups.
Hunting: This one is fun. Since your armor is faster than most others (Sparing an Infiltrator or upgraded Ariborne), you can chase whoever decides to flee you. Using the gravity gun to go faster, you will probably outpace even some airborne armors. Most people probably place priority on defense or targeting over speed, so you can probably outpace upgraded armors or other Exoquatics. Shoot at them as you go. Using this strategy, I have chased another Exoquatic around Knox, frequently outpacing him, without use of an accelerator, defeated him, and never once got shot. Reccomended for use against the survivor of a big brawl.
Distance Shooting: I use this against Hellfire users who have found or stopped me from sniping. Simply stay at a distance and aim near him, and you should take them out in a couple rounds. Not reccomended if there are multiple rocket-armed enemies in the same room as you.
In any of these cases, you don't have to be very accurate, as your projectiles are quite large, and will bounce, taking out some of those who dodge your original shot.
I will add map-specific and more strategies later.