I confess that having James disable the AA guns while saving admiral Koris still makes me laugh as much as it did the first time.
Also, I always scare Boo at least once with the husk head from Bryson's lab.
That husk head was a huge missed opportunity for Bioware. This was an M rated game after all but I know kiddies play it. But Shepard is supposed to be losing it as the game progresses. He/she has no one to talk to. Everyone is dumping their problems on Shepard. So the way I figure it, between missions (any mission) Shepard could have gone to his desk, or liquor cabinet, and pulled out the head, red sand, or some booze, and fired up a cigarette. Sat down on the couch, and put the head on the table. Then either done a couple lines of red sand or knocked back a couple shots of whiskey and had a talk with the head. Just a Shepard monologue b*tching about everything that's happened so far. You get two autodialogues of b*tching. Nothing is sacred. If you want to do more, you've got to drink more or do another couple of lines for that extra special one. But then you've got to return to duty.
But remember, the more you do, the more likely you'll lose control over YOUR Shepard, and after a mission your Shepard will head up to his/her quarters and drag out the head and red sand or booze and starts smoking. Then during the Battle of London -- Shepard in cover fires up a cigarette, and leaves it in the corner of the mouth.
Then in the completely lost it category - asks TIM for a cigarette on the Citadel. Then... "any red sand?"
Then the ending may have made sense.