Use quite a few myself. ZDoom/GZDoom for most limit-removing/Boom focused levels or Eternity Engine/PrBoom+ if running into problems (Asylum of the Wretched). Then I play most classic/vanilla intended levels in Chocolate Doom, it just feels so much nicer doing so. 

I played some Knee-Deep in ZDoom coop with Daz and rebb, and some Plutonia 2 coop with rebb the other day. It was good fun and surprisingly easy to set up - that is, after working through several network issues like port forwarding and out-of-sync sessions.

We found that Skulltag (and Zandronum) work suitable well for simple coop and dm games. The ports have improved netcode over ZDoom and an inbuilt server window which allows for all kinds of tweaks that seem to take effect immediately.

Hope to get some more games going. 

zdoom is the only port i play doom with. gzdoom, at least the early versions, was too nasty looking [blurry as hell]. i guess by now it must be pretty neat, but i cant be bothered downloading other ports.

so lazy to get other ports that sometimes i miss wads intended for non-zdoom ones :D 

GZDoom gives you really good control over how much, if any, texture filtering you want.

The main benefit of GZDoom over ZDoom for me is that I don't want the Z-warping when looking up and down.

(But maybe some folks like the warping, or they don't look up/down, or whatever). 

Zdaemon is worth trying with, unless thats what you mean by Zdoom...
http://www.zdaemon.org/