Sick Boy and Renton casually, almost disinterestedly watching the home porno of Tommy and his girlfriend. Of course, Harsher in Hindsight when the theft of the video inadvertently leads to their breakup and Tommy's downward spiral and eventual death.
Renton shooting the dog in the nuts with an air-rifle.
Sick Boy: For a vegetarian Rents, you're a fucking evil shot.
The bed sheets scene. Nausea Fuel doesn't quite cover it.