Here's a bit of secret knowledge that's also nearly useless:
Units have a hitvolume, this determines where a projectile has to pass through to hit them. They also have a hitcenter (don't know the real name), this is where enemy units will aim at.
Now, units also have an emitweapon (don't know the name) point. For some units, the line along which it can fire its gun and it's emitweapon point does not pass through the unit's hitcenter. (analogy is an annihilator with a hitcenter inside the big box while the laser comes out the gun on top)
This results in strange things like a glaive behind an enemy mex being able to shoot an llt on the other side of the mex while the llt can't shoot it. (only valid on some angles, I think the glaive has to be almost hugging the mex)
Other situations with terrain and blocking may also appear.
This is very rare and quite impossible to deliberately use.
...
A more useful secret is: spread your rogues (shield bot skirmisher)
Rogues have an emitweapon point that is outside their hitvolume. When you pack rogues together, they will collide with each other and when they fire, may actually hit each other instead of actually firing. (I'm not sure why the friendly-fire safe rule doesn't apply to them while it applies to other units)