A suffix added to the end of a word to signify that you are throwing that person or object at someone as an attack. It is usually yelled while making the attack.
In Japanese 'douken' literally translated 'motion fist.' This was first popularized with the move 'Hadoken,' first appearing in StreetFighter, meaning 'wave motion fist.' The present use of the word has its roots in the webcomic 8-bit Theatre, in which one of the main characters, Black Mage, is able to use the move 'Hadoken' once per day. In one strip, having already used his daily attack, he comes upon the idea to hurl his companion, Fighter, at an enemy.
Jon grabbed Chris' backpack and threw him at Serge, yelling "Chris-doken!"