Curtains Down is probably my favorite...there's multiple ways besides switching the gun though, you can equip either your sniper rifle or silenced silverballer (from the balcony or behind) and shoot him as the actor pretends to fire the fake gun...or simply snipe the dude in the balcony from behind the stage.
One accident I really like is in Till Death do us Part where you push 'Pappa' LeBlanc into the swamp, a gator then devowers his body...very cool.
Plus the sabatoge of the piro on Vaana in A Dance with the Devil (I never really understood the layout for this mission until I saw Eyes Wide Shut, now I get where they got the idea from)
In Curtain Call or w/e its called, when you hide in the closet and wait until the guy goes to the toilet swap the guns and then just walk out and go to the nearest set of big doors. In there are a few workers and a flight of metal stairs. Go right up top on them and go through the door. You will be in the attic, just above the auditourium. Place a bomb where it says in the center. RUn down, get your normal clothing back on and go into the auditorium and watch the shooting from behind all the seats near the door and pull out your detonator. After the shooting, you will see the American Ambassador panic and run into the auditorium. When he's in the center, pop the bomb and the chandellier will fall on the ambassador. Then just walk out calmly and walk out of the building. These will both be classed as accidents. TADA!!!
All times are (GMT -08:00) Pacific Time (US & Canada). Current time is 6:31:23 PM