played version 1 last year at another lan and i think this would be good for a "change", it does require half lfe 2 deathmatch , which is free if you have half life 2, so first dl that and then get the client files and the client patch(both nearly at top).
had really good fun with this and now its been upgraded to source, so if you like the idea click the link, i will also have the files incase you cant be bothered d/l ing it, but you need half life 2 deathmatch installed!!!!!!!!!!!!!!!!
http://www.bgmod.com/
do it now