Assuming you have several magazines (at least 3, each holding 12 or more darts), I would suggest either the Stryfe or the Retaliator...maybe take both and you can see which you prefer.
Most people will probably pick the stryfe over a retaliator, especially since you haven't converted the retaliator to pump action.
Before you take the stryfe with you, remove the dart sensor (if yours still has it). It's the part with the spring pictured here. You literally just unscrew the blaster, pull it out, and then put the blaster back together.
Many HvZ events limit blaster performance so the Big Bad Bow might actually not be allowed.
The Doominator might be your best bet if you don't have a lot of magazines.
Range isn't too much of a factor since the zombies will be rushing at you. So make sure your blaster is reliable and easy to reload with lots of darts.
Other people that have played a lot more HvZ than I can give you more advice, but that should get you started. Good luck!
PS: Assuming they allow you to use balled up socks as (thrown) weapons, make sure you take some socks, too.
Edited by jwasko, 24 October 2016 - 07:02 PM.