One of my favorites is the medieval rondel dagger. I typically make these using 5160 steel with a thick spine and single bladed edge, with rondels made from wrought iron.
I've made many other styles of daggers including large double-edged gothic, slender stiletto, sword-hilted double-edged, and on, and on. I'm up for just about anything on daggers. Go to the Gallery page to see most of my latest creations!