I think I've said elsewhere that Tom's exit affected me like no other, like bertowud I empathised with it. But it's Zaf that really breaks me. As Jo says "Zaf [died] alone in fear and agony" and his last act as an agent that we know of was to save Adam with the grenade, and that beautiful shot of him from directly behind his head.
I do find Colin and Ben moving though, not because I particularly liked the characters but because is there anything more senseless than being killed by someone who's meant to be on your side? Even more insane than strapping yourself to a bomb.
And I find it so sad that scene with Malcolm, Harry and Adam responding to Colin's death. It makes me cry every time.