Plasma Carbine on most of the Unidrons are a fearsome weapon on a line trooper even one with poor BS. For additional SWC one can also purchase a Spitfire, K1 Combi Rifle, Plasma Sniper, or Shotgun and Missile launcher. A FO model is also available giving the good combination of a Plasma Carbine for close range and Flash Pulse at longer. On top of all of this Unidrons can be given support-ware programs, and are linkable in the Onyx sectorial army.
A pistol and knife completes the usual package, but Unidrons want to avoid CC whenever possible.
1 armor and Dogged are about their only defensive tricks. Being REM models they cannot go prone so lack one of the more essential defensive strategies. Due to their BTS stat, the Unidrons have more defense against hacking than the typical REM model.
Support-Ware on a Unidron can really up their power level.
Unidrons posses both Dogged and Structure which creates a weird interaction. When a Unidron goes unconscious, it can opt to stay unconscious or go dogged (and pass to dead at the end of the current player's active turn). However, since the Unidron has structure it has a second unconscious state (hereafter unconscious 2). This does not mean you get 2 wounds while in Dogged state. It does mean that if you take two wounds in one set of fire, thus passing from normal, to unconscious, to unconscious 2, you can chose to go Dogged while in unconscious 2. Effectively, it will take one more wound that normal to remove a healthy Unidron immediately.
Also, because they have Structure instead of Wounds, the Unidron Batroids ignore the "pass straight to dead" effect of Shock and Viral ammo.
The usual tricks of Shock and Viral against dogged models don't apply here. Instead you will need to plan for weight of fire or an extra order or two to remove the Unidron Batroids. This can make them really annoying ARO turrets, especially with Support-Ware. If you can, take out the link over multiple turns, putting a model into unconscious or dogged, then working another part of the table. Also, if you do have a chance to shoot an unconscious Unidron, it is almost always worth it (unless there is no engineer on the enemy force).
Stacking modifiers and relying on weight of fire should help. Just be mindful of the many Templates that a Unidron Batroid link team can put out, and be careful with your approach.
Also keep in mind that Unidrons are remarkably resilient to hacking attacks with their BTS and a Tin bot on some profiles.
Unidron Batroids make good cheap additions to a list as order fillers or cheap specialists (the FO has the added bonus of being pretty dangerous at short range and can go dogged while scoring an objective). Generally a single Unidron with a SWC weapon is not as efficient as similarly priced models in Combined Army such as the Haiduks or Noctifers, but it can still fit some builds.
In the Onyx sectorial when running a Unidron Batroids fireteam the K1 and Tin Bot model deserves special notice. Not only does it protect the link from hacking, but the a linked K1 combi is dangerous against most targets and a real threat against TAGs and HI.
During Deployment keep in mind that the Unidrons cannot go prone, meaning they have less places to hide than the average trooper, and should they need to retreat via a failed guts check, they will have to do so while standing.
Active Turn Role
In a fireteam the Unidrons will accompany a Nexus or Umbra to the fight, or act as the link leader themselves. When not in a fireteam, they will either be holding back and protecting short approaches, or, in the case of the FO, useful as a throw away specialist to score a dangerous objective.
Choosing when to activate dogged is important. If the enemy has few orders left and you have access to an engineer, it can be worth not activating Dogged to repair the Batroid. As far as plasma ammo is concerned, they make a good ARO deterrent from short ranges. Dodging should be avoided in most cases due to the -3 to PH suffered by REM models, but against heavily modified shots (say against an enemy TO model, or a sniper in cover from a very long range) it can still be worth it to dodge and live another day.