Manuel Mendoza

Private Manuel Mendoza was one of the Marines who survived the crash landing on Installation 04. He was part of Fire Team Charlie who where led by Captain Keyes to find the "weapon cache" that they thought the Forerunners had left on the Halo. Instead, it turned out to be the main holding area for the Flood, and all of their team, save for Sergeant Johnson were taken by the Flood, and absorbed into Flood forms. Mendoza was the smart one, he attempted to escape the room; but the Flood were able to infest him before he did. The Master Chief noted in his debriefing that he had an encounter with Mendoza as a Flood form while on the Halo, and was forced to kill him in self-defense.

Trivia
There is also a glitch in Halo: Combat Evolved that allows you to get back on board the pelican and once the pelican lands, if you just run along the perimeter, eventualy you will find Pvt. Mendoza just standing there in the middle of no where.