• Warmduscher, Weichei, Lump - wuss
  • Knalltüte - literally "bang bag" (somebody who's not to be taken seriously)
  • Trottel, Blödel, Dödel - sap (the last one actually means "dick" as well)
  • Pisskopf - "piss head"
  • Schwachkopf - imbecile
  • Arschgeige - "arse violin" ... thanks to RalphyK for reminding me :)
  • Arschgesicht - "butt face"

Those were in rough order of increasing offensiveness. A guy from South Tyrol (native speakers of both Italian and German) once told me that German is rather boring compared to the colorful possibilities of Cussing in Italian. But still, every few weeks I've got a new swearword of the month :)