Multiple rounds. To the head. Gruesome, but it is the only way to ensure a quick death. Don't believe the movies - a single round is rarely enough to kill instantly - there are even numerous cases of people being shot through the head and surviving.
Poll
What is more sane?
| shoot just once to not ruin dead body | 31% | 31% - 16 | ||||
| shoot multiple times to ensure quick death | 68% | 68% - 35 | ||||
| Total: 51 | ||||||
It never takes just one shot.