On halo combat evolved, there is a mission where you encounter the flood and you're backed up by some marines, there are two paths. One behind a rock and another crossing a lake, the rock path apparently leads your team away from some of the spores that will infect them, but the other path...
I changed paths before the Friendly AI could think so they took the wrong damn path, all I could hear were the screams of at least 20 marines as they had infection spores drilling into their chests and combat forms lashing at them with tendrils and plasma weapons.
I'll have to get images by replaying the level and doing everything exactly like I did before, but to give you a mental image of what its like, I'll just have to show you this.
What makes things worse is that I was playing on Heroic at the time so their health was cut 1/3 making them weaker.