I surprised myself last night. I was looking through the achievements and thinking some of them would be kind of hard to get. Jump Shot is headshotting a hunter as he leaps at you or anyone. I thought, man that would take some pure luck to get that achievement. It just so happens that luck was smiling on me. A few minutes after thinking about all this I happened to randomly headshot a hunter, with the hunting rifle no less. It wasn't an aimed shot. A bunch of zombies were swarming and a hunter was there too. I popped up the scope and fired randomly and I unlocked the achievement. Super!
Sorry to rain on your parade but Jump Shot was one of the first achievements I got, and other people seem to be getting it all the time. ;P
Now the one where you have to PUNCH a leaping hunter.... that one's got to be hard to come by.