I use this because it is the simplest one with the least extra bullshit. The few visual additions (fog, skybox, coloured lighting) are fine when done well, and I really don't want anything more.

2nd place is RMQ, only when the map forces me to use it. 

I've been using Tyrann's software engine, which supports bsp2 and helps me pretend like its 1996. 

 

My name is onetruepurple and I use fitzquake5.exe most of the time. 

My name is mfx, and I use QuakeSpasm 0.85.9.
2nd is fitz 0.85.
3rd choice is the engine Ijed mentioned. 

...unless a release calls for a specific engine to run. 

1st: unreleased engine. based on joequake with fitz,bjp,etc parts and influences.

2nd: quakespasm, usually freshly compiled from svn. 

which is DirectQ 1.9.0 

I used fitzquake as a close second 

My name is ScampieSUXCOCK and I use Quakespasm. 

And I use FitzMkV, or RMQE 

I remember an earlier version I tried did not animate the sky textures correctly on func_walls, which was something I had done in Castle of Oblivion. So I stayed with GLQuake for a while, but I think with 081 I switched for good. 

for a long time i've been using aguirres enhanced engine

and now i use fitz85 (modified to prevent that infamous "whats that name of willem map" bug) 

Lately I have been using Fitz mark V with bsp2.
And Tyranns engine, as second engine. 

 

This would have been a great discussion thread!

Anyway I use Fitzquake latest SVN version (which is basically 0.85 with 2-3 half-baked new features) 

I vacillate between fitz .85 and the RMQ engine. 

I AM SCAMPIE I USE QUAKESPASM

Mostly because it's like Fitzquake, but also plays .ogg files from /music/ 

My name is Tronyn and I tend to use Jack Danieeaas I mean FitzQuake but with a strong secondary reliance on both DarkPlaces and RMQengine 

I am JPL and I have two reference engines (aforementioned)

I personally use both of them depending on the map. No need to say FitzQuake is the reference engine I (have been used to) map with. but I always give a try to aguirRe GLQuake, because it has a different look ingame (i.e light and fog density are not rendered the same)..

Well... Fitzquake is my preferred engine in anyway ;) 

Also, FitzQuake 0.85, because it comes with no bullshit and I haven't found a reason to use anything else yet. 

Some would say 'bloated'... 

and I used FitzQuake0.85 all of the time 

Is nice and rounded engine, but I can't use it to play my maps.

I use it when I record demos for others.