I'm not jumpy but my DH is.
It's so much fun scaring him and making him jump.
He is usually off in his own little world and ignoring everything so it is quite easy to sneak up on him and just stand there and wait for him to turn around and see me. He screams, and I laugh! Even our 2yo daughter is learning to hide and/or sneak up on him and say "Boo!". She has genuinely scared him sometimes, and she cackles her little head off.
At our previous place I would hide on the staircase just inside the front door, wait for him to open the door when he came home from work, and leap down at him. Scared the hell out of him, and he nearly collapsed in fright. He learnt to be very wary when opening the door after that. I would also sometimes hide in the wardrobe when I knew he was going to open it.
It is so funny to scare a jumpy person! To all of the jumpy people, try it and you'll see why we love to do it to you, and find it so funny!