Day of Defeat is a really cool Half-life modification. It features fantastically detailed World War II maps, weapons and Playerclasses, one-shot-kills, Stamina guages, among other things.
It's one of the best Half-Life modifications, consistently rating in the top five multiplayer lists on Gamespy and WON.
A haven for counter-strike refugees, it is favoured because of its realistic playstyle and gameplay mechanics... Players can be gunned down in an instant upon leaving cover, so everyone is always crawling along prone, strafe-jumping past corners, etc. Bunnyhopping is disabled by a stamina-counter, which (fortunately) only measures jumps, not running or anything else.
It favours newbies more than Counter-strike, as respawn times are usually in the 15 second range, as opposed to 5-minute waits. However, many, many kills are achieved through camping, sniping, and "cheapshots". While this does sort of echo reality, it can be frustrating to be sniped by someone with their torso embedded in the cliff-side.
Games are highly tactical... Rushing is frowned upon, and often leads to low kill-counts. Allied and Axis teams have completely different player classes with different guns, grenades, etc. Often, the Allied light-infantry will rush with their fast-reload, one-shot-kill rifles, while the superior Axis Snipers and Machine gunners will hang back. Grenades play a very important role, as campers will often have their backs covered by team-mates.
The settings are immaculately detailed. Most maps are command-point based... Each side is trying to capture as many flags as possible. Staples such as dod_Caen and dod_Oslo are favoured considerably. However other maps can be more interesting... dod_Omaha includes allies storming a beach, while being sniped at from pillboxes. Player models vary from traditional Blue vs. Red skins, which can be difficult for newbies. Each class has different camouflage, although the Allies tend towards lighter garb, while the axis stick to navy and dark green cammo. A nice touch is that all the axis voice-bindings are in German.
The game is extremely fun, after the first hour or two of play, which can be difficult.
It can be downloaded from any good gaming site, or http://www.dayofdefeatmod.com/