I was thinking either:
A ) When selecting a target to shoot, a line is drawn from the soldier to the targeting reticle (like a laser sight). The laser stops when it hits an obstacle, so you know if there's anything between you and what you're aiming at.
B ) When you try to shoot somewhere you don't have LoS on, you simply get an error, like in the original XCOM.
I've been screwed over too many times by shooting HE at a guy below me, and blowing myself up, or wasting buckets of ammo and TUs turning a wall into swiss cheese because my angle of attack is slightly off...
Edited by Emerald, 16 March 2008 - 05:14 PM.