My main collecting fancy are Demonstrator pens. Here's a photo of some of the German ones in my collection:
From left to right: Diplomat 100 Demo, Ero Green Demo, Geha 708 Demo, Kaweco Cutaway Demo, Lamy 27 Demo, Lamy 46N Blue Demo; Luxor Demo, Matador Click Blue Demo, Reform Skywalker Demo, Reform Pharoah Green Demo, Rotring Tintenkuli Demo, Senator Clear Dmo; Senator Rose Demo, Soennecken S4 Deno, Soennecken S4 Blue Demo and last, Usus Io Demo.