I'm playing through Mass Effect again (this time as a marathon through both games), and for the first time I realized I could save (minor spoiler) the salarian commandos on virmire. I didn't even really realize it until I ran into them on the normandy afterwards.
it was almost the same kind of surprise which I liked about Deus Ex, where I found out after 6 playthroughs that I could save (bigger spoiler here) Paul
I know, after the fact I realize that it was a bit obvious in ME if you watch the minimap but overall I love when games give you options outside of dialogue trees, and also outside of "go left or right down the corridor". more designers should do stuff like this in games!