Taking someone out from behind

[Kinjit]

1. You want to take down and control the attacker without causing too much damage.

2. You want to take him out as quickly as possible, doing maximum damage (empty handed).

2b. He is holding a weapon.


I know these examples are pretty vague, but I'm thinking in general principles here. What kind of strikes, chokes, techniques etc do you think are effective ?
I'm not a very experienced martial artist myself, but I'd probably go for a sloppy rear naked, pulling off balance with a knee in the back etc...