I looked through the Image Directory, and there was no GinTama (And since I've contributed so little... sweatdrop )
GinTama is written/Drawn by Hideki Sorachi. It's a comedic manga that focuses on the lives of three "Yoroyuza" (Freelancers, basically) and their trying to get by in a Japan filled with aliens (Amanto). Politics, fighting, samurai, and SciFi themes are all intermixed in it, as well as a cast of memorable characters.