Whatever mod the server ends up as, I'd say make it non-passworded. probably res-slot. I think that's why the CS server is unused.
As far as mods go, I'm not too particular, mainly because as a dialup player, i don't download mods much. But here's my 25 cents anyway, kinda in order of preference.
Day of Defeat. Gotta love cooking off nades.
Half-life. Unmodded. Yes, i'm talking plain old Half-life deathmatch. Freaky, ehh?
The Battlegrounds. Revolutionary war mod. As in 1776... It's got the whole 1 shot and 20 second reload thing goin for it. Not sure if it's steam supported though, as i think it's dev community died and is now opensource. Haven't checked it out in a while.