So, a weapon with thermal only effects?
I can't help but think of those grenades from the movie Blade (or was it Blade 2 or 3?).
Lethal sunburn that fits in a pocket.

Perhaps make some sort of device that uses a combination of IR and UV energy and other prompt radiation forms (perhaps including microwaves) to both deliver a large amount of heat or otherwise causes a reaction to generate heat within affected objects (such as anything with water in it, in terms of something like microwaves)

Being the DSTech troops are all robots, a little radiation probably won't bother them at all.

Well like the Blade ones I suppose, having never seen the movie, but on a nuclear bomb scale. I mean a nuclear bomb minus explosion and anything apart from the giant burst of light that melts clothes into skin and turns people into ash silhouettes on walls.
I'm thinking checking each actor for line of sight to the explosion by rays or something, then dealing health damage based on distance, spawning ash particles proportionate to health lost. Actors that hit 0 health gib.

Erm...
Similar ideas I suppose, quite different implementations though.

If you play with the code you could probably make it do less with the ashing effect as the 0hp point you mentioned. Question is how would you make it act like rapid thermal pulse without just blasting the actor to ashes. OOoh have the impact of a semi visible or invisible wave give off particles and make the weapon spawn a contuining effect for a couple of seconds. That could work would be pain to make work properly.

Hmm...
Yeah, you probably could make the microwave gun's effect the zero hp effect, but my suggestion is significantly less laggy on units in air. Though I'm against a non-instantaneous thermal flash: the heat is conveyed by visible radiation - it travels at the speed of light. Any continuous or delayed effect is not accurate and your suggestion would probably be more laggy and less effective, assuming spraying enough particles everywhere to affect everything in line of sight takes more processing than checking each actor for line of sight to a single point.

Hmm true that would be lag tastic. Possibly limit the number of directions and *particles/rays what ever. That the weapon emits but have the impact be are of effect that causes the ashing part. You could have the burst emit only a few particles at a time with a rapid decay to limit range and lag effects but have just enough to make it dangerous. Or we could go with the ray gun effect a shot that can cause it. All of this of course is limited by that nasty lag thing.

No.
Lag is not necessary.
You cycle through the actors once, at the explosion frame and use a single ray each to check if they are within line of sight of the explosion.
That would produce next to no lag compared to what you have been suggesting.

I was thinking of a single ray solution but couldn't figure it out. That does make better sense. But could we make a bomb do that? Including handling coding for various obstructions such as affecting the soil grass and structures differently with that check or would it ignore those and not apply the damage to them?

It's seriously not that hard.
Cycle through actors.
Use trig to find the relative angles between it and the explosion.
Cast a ray from the actor or the explosion (from the explosion would probably make for neater code) to the other to see if there's no obstruction.
If there isn't then apply damage and spawn ash according to distance.
And yeah, it's been edited now, but I meant one ray per actor.

Ahh one ray per actor. That makes more sense. I was thinking of some how making the one ray sweep around a set point and any actor it touched would have the damage applied. So basically at a weapons activation it does a quick check and any actor that is considered in line of sight gets a ray drawn to it then the affect applied.

The ray is to check whether or not it's in the line of sight.

Doh Ok ray first and any actor that gets the ray gets the effect. Im a lil tired from work so my brain is on half speed.

That's not quite it either.
There's a code structure that applies code to every actor on the scene.
We're using that to check the position of each actor and comparing it to the position of the explosion.
Using trigonometry, we find the angle which is required to draw a line from the actor to the explosion.
We fire off a ray along this path, seeing if there is something in the way in between the actor and explosion.
If there is nothing, we find the distance between the actor and explosion, using that to calculate how much damage to do as well as how much ash to spawn.
So instead of firing rays out of the explosion to see if they hit actors, we are cycling through every actor and firing a ray from the actor towards the explosion to see if there's anything in between.

Allstone, I can't see why you even bother.