Robar - I shoot competitively every weekend. The three timers that Jack posted from Brownells are the ones most used. I use one of all three usually throughout the month.
Years ago I bought one made by Pact not shown which not only times, but you can hook up sky screens and use
as a chronograph. It is a little big, about twice the size and the "pact club timer" shown and $100 more.
It's the one you see Jerry Michulik ( sp butchered sorry) using on Impossible Shots.
I don't use it much any more, I decided for a much more lighter, smaller unit, so I went withe CED 7000(the one on the far left). It is the lightest one out there.
The other benefit of the CED7000 is there are a lot of accessories that you can get.
I bought, a car charger, a double A battery charger for out in the field - that saved our bacon at a match when they forgot timers and I had mine, but the charge was low. I plugged in the AA charger/piggyback and was good to go.
I also got a rubbler slip on cover for gripping and protection - like you get for your cell phone.
They have and arm band available and a lanyard.
These accessories are not available with the other units to my knowledge. If you use the timer as much as I do, it is a Big plus.
Let me know if you have and questions.
Good Luck