When you lose a squad member in XCOM: Enemy Unknown, you lose them for good. And one of the dastardly things about the game is that as you upgrade your weapons and armour, so too does the enemy. There's never a time when you feel comfortable with putting your veterans' lives at risk. One user found a way to circumvent that - beat the mission with just one unit!
I recently started an Ironman Classic run with most of the random settings released in the new update, and I've repeatedly had my entire squad wiped out as I work my way towards better armour. So this is... Inspiring.
As you progress in the game, you do get the ability to bring combat-capable robots in place of humans. But they're limited in what they can do, and I found their most useful feature was as mobile cover. Plus, they don't have the ability to pull off stuff like this. The secret? Psionics: