Technology you don't bother using

[JakeGrey]

* Non-Project bodies: I find the default, all-rounder bodies to work just fine in campaign and skirmish alike.
* Hover propulsion: Their speed doesn't make up for their fragility.
* Hurricane AA turret: Needs multiple upgrades to reliably bring down enemy aircraft before they drop their payloads, especially in the campaign.
* Inferno/Plasmite turrets: The standard flamer is a niche weapon at best, and the extra DPS doesn't really justify the cost.
* Radar detectors: Probably ought to start a whole thread about these, but if I even see them in the research menu then I've probably got control of the map anyway.

[aubergine]

Easier to say what I do use...

Structures:
Walls (and gates in recent versions)
Sensor tower
Hardened sensor tower
Wide spectrum sensor tower
Satellite uplink
Mini rocket tower
Lancer tower
Flashlight / Heavy laser emplacements
Gauss cannon hardpoints
Mortar pit
Howitzer emplacement (as a stop-gap until I get hellstorm)
Incendiary howitzer emplacement
Hellstorm emplacement
EMP mortar (the EMP Cannon Tower is useless in comparison)
Ripple rocket battery
Seraph missile battery - these have got so much better in recent versions!
Archangel missile battery
Hurricane AA site
Vindicator SAM site (and hardpoints)
Stormbringer emplacement

I also use all the fortresses, LasSat, and other common base structures with the exception of CRC.

Bodies & propulsion:
Viper, Cobra, Scorpion, Panther, Retaliation, Retribution. All propulsion types.

[Shadow Wolf TJC]

Personally, my playstyle tends to focus on wearing the enemy down through attrition, emphasizing speed over armor, and armor over firepower, attempting to harass the enemy at various points, but trying to preserve whatever forces I can. As such, I tend to favor using Cyborgs, Hovercraft, and VTOLs over Tracked units for offensive purposes. That way, if my units take too much damage, I can quickly send them back for repairs, and I can even choose which range I'd want to engage my enemies at. For this purpose, I've chosen to specialize in the Mortar line, as well as the Cannon and Machinegun lines due to the fact that Light Cannons are a research prerequisite for Mortars, and so that I'll have a balanced selection of weapons for dealing with a wide variety of opponents, from Lancer Tracks to Cyborg Flamers.

Here are the following technologies that are low in priority in terms of me researching and/or using:

• Almost everything in the rockets/missiles line, including Lancers, Ripple Rockets, and Archangel Missiles: As powerful a punch as they may have, which is great for precision strikes or some quick, cheap counter-battery work, they tend to be more difficult to use effectively in groups than cannons, machineguns, and howitzers due to their tendency for overkill.
  
  Tracks: My playstyle tends to focus more on harassing the enemy than on rushing or steamrolling them, so speed is more important for me than armor. Besides, if I see tracked vehicles approaching my base, I might pelt them from afar with Mortars and Howitzers, and/or swarm them with Cyborg/Thermite Flamers. That's not to say that I don't use Tracked vehicles myself. In fact, I do like to use these in addition to Hovercraft, Cyborgs, and VTOLs, though in a more defensive manner, including counter-battery purposes.
  
  New Paradigm Bodies: Since I tend to prefer speed over armor, and armor over firepower, The Project and Collective bodies suit my needs better. I could always look for a lighter alternative if my preferred weapon mount slows my units down too much.
  
  Flamer Bunker: Short-ranged weapons like Flamers are best mounted on fast units like Cyborgs and Hovercraft, not stationary buildings like these Bunkers. I'd probably want to keep my distance from these anyways, and pelt them from afar with artillery, or even machineguns or cannons. The only use that I'd find for these is if there was a big bump in the way to obstruct line-of-sight from longer-ranged units. Speaking of, bunkers are themselves very weak to Flamers, so I doubt that these would be useful at all against a rampaging horde of Cyborg Flamers.
  
  (Twin) Assault Cannon: A rapid-fire all-rounder weapon that has more trouble making a dent in heavier armor than a Hyper-Velocity, Heavy, or Gauss Cannon? Yeah... I think I'll pass.
  
  Plasma Cannon: As powerful as they may be, they're far too heavy to be worth mounting on most Hovercraft, and thus using for offensive purposes.
  
  Nexus Link Turret: I don't know how long it takes to assimilate enemy units or structures, so I tend to skip over this.
  
  Emplacements and towers in general: Emplacements typically have FAR less HP and armor than hardpoints, so why the heck do they cost more? I don't get it. As for towers, they're slightly less expensive than hardpoints, though they're still FAR less durable. Because of this, I tend to steer away from researching either of them, UNLESS its the Machinegun Guard Tower (which is great for securing oil derricks very early in the game), or there aren't any other structures available that can mount my desired weapon or system (which is true for artillery and sensors in general).
  
  Heavy Rocket Bastion, Missile Fortress, and Mass Driver Fortress: Out of all the fortresses in the game, I find that the Cannon Fortress is the best for me, due to its high dps and splash radius, even against the most armored units in the game, and this is all coming from the least expensive fortress in the game. The Missile Fortress would probably come in 2nd place due to its long range, but since I'm not prioritizing rockets in my tech tree, chances are that I won't be building any of those until very late in the match, perhaps later than when I've already researched Dragon Bodies or the Laser Satellite Command Post.
  
  VTOL Strike Turrets and Towers, and VTOL CB Turrets and Towers: Why do I even need them? I could just manually order them to fly over to whatever target I want them to attack.

Edit: Forgot to add emplacements and towers on the list.

Edit #2: Added VTOL Strike Turrets and VTOL CB Turrets onto the list.