The German word for comrade, a fellow soldier. But that's not all. It's worked its way into English (well, almost) under a very different meaning.
During World War II, German soldiers would yell 'Kamerad!' to American GIs to signify their surrender. Techincally, it simply means 'fellow soldier', but when a guy with a gun is coming at you, any word that could be interpreted as 'friend!' or 'I give up, I'm on your side now!' will do just fine.
The word was used this way enough for the Americans to decide that it basically means 'to surrender'.
'Kamerad' is also a surname. Very rare in the United States.
Sources:
http://phrontistery.50megs.com/k.html
http://www.thedropzone.org/europe/Bulge/williamson.htm
http://groups.google.com/groups?selm=q9oh01m5p5.fsf%40lili6.lili.uni-bielefeld.de
http://www.newsday.com/extras/lihistory/vault/wwilett.htm