There are just so many missions in the old republic, but still I remember one mission or two that have stood out among the others!
As a Jedi Knight there's this one side-quest at the very beginning (that's extremely trivial and has nothing to do with the plot in any way) that involved finding out about two jedi trainees who are supposedly in some sort of secret relationship. That one stuck out to me because it was the first instance when I had to make a choice I didn't want to make just to get light side points.