Honestly, I could go on for ever about Blood but I'll keep it short. It is insanely fun, and well designed and was actually the first to innovate a few now common FPS features... like alt-fire modes. Sure somegames had it on a few weapons but this was the first to have it for all weapons.. Really allyou need to know is : You're a vampire/undead outlaw cowboy in a trenchcoat that can dual wield tommy guns and play zombie head football.
It's not the best of the dungeon crawlers, and it has many of the same problems but it is still a pretty nicely done one, certainly it will challenge and frustrate you but in the end that's what you expect from this genre. This game tried some new things, not all of them worked but you can see that there were attempts at innovation. So glad I voted to get this added here :)