If you've seen my other posts I love thinking about questions like this...
If you could only pick one primary mechanic in games you own which would you pick and why?
I'm sure most people can guess that Area Control would be mine. I love Area Control because it often requires negative player interaction. I also like a map that gets smaller over the game and feel like it helps create tension throughout the game.
What about you? What's your one primary mechanic?
I think I can guess @theDL's answer.