I have a ProChrono Digital, a Shooting Chrony Alpha Master, and a Pact Mark 4 (which is a shot timer that doubles as a chronograph with accessory sky screens).

I use the prochono the most. Not sure why, I suppose because it was my first, and it's very easy to use. The company I was working for at the time let me keep it after one I completed a project, developing specialized ammunition. Been using it for 10yrs now, everything from archery at 200fps to super-speed centerfires at 4000fps.