Superman's famous heat vision, which he usually uses as a "utility power" for things like escaping something, freeing someone, or other uses. If he ever uses it as a weapon against an enemy, it's usually against a robotic or other nonliving enemy (because Superman adheres to Thou Shalt Not Kill). Him using this power is also usually a sign that you've truly pissed him off.
Superman (to Mongul): Burn.
- In the Silver Age, Superman had to wear glasses made from Kryptonian glass in order to use his heat vision while disguised as Clark Kent (otherwise the glasses would melt); Post-Crisis, this power was reinvented as pyrokinesis and thus that's not necessary anymore. Naturally, the TV versions tend to simply discreetly move his glasses out of the way.
- Originally, the heat effect was just supposed to be his X-Ray vision turned up full blast, so during the 1950s and early 1960s, it was always described as using "the heat of my X-ray vision." Heat vision finally became a separate power in 1961's Action Comics #275, and has stayed such since. (Some Silver Age and Bronze Age reprints of stories using the earlier phrase would awkwardly reword it as "the rays of my heat vision" or similar.)
- Post-Crisis, Superman's use of heat vision changed markedly, as he was now a solar-powered superhero. Using heat vision came out of the same energy bank that all his other powers used, but at a very steep cost. Now heat vision was used sparingly or only once a battle. Really cutting loose with the beams now means that Supes is NOT in his happy place.
- Remember that bit in the cinematic trailer of DC Universe Online? He MELTED Black Adam's face off with only a guttural yell. Scene in question