I decided to try Skulldash
http://joshuaosullivan.co.uk/skulldash/
I'm really enjoying it. It's Doom with another layer of gameplay added on top of it. You have to collect coins that are placed around each map under a time limit. You don't need to collect all of them to unlock the end of each map, just a set number, but if you collect all you unlock additional secret. Some of them also add additional time, others also act like vanilla Doom pickups giving you bonus armor or health...
All maps are accessible from the main hub area
Weapons and ammo don't carry on between maps, but IMO that isn't a big deal here, and all maps are meant to be played from pistol start.
What I really liked is how so far (I finished first two "chapters") each map had a unique theme and sometimes its own gameplay gimmick. The ice in this map is slippery, so movement and platforming require additional care:
They all look nice and are cleanly detailed, with lots of source port effects on display. There are other new gameplay enhancing features too, for example jump pads and fans that lift you up. Their layouts really feel like those of deathmach maps, which suits the mod's gameplay.
Only map I disliked so far was this one
I liked the look of haunted mansion and use of Blood textures, but it was frustrating to play due to number of stealth monsters and lack of health.
There are also some boss fights, I encountered the first one after I finished all maps from second chapter.
Some more screenshots:
As far as I'm concerned this is
if you don't mind something very different and gameplay designed around time limits.