Best looking is very easy for me. Ed Schempp's Persian, gets my vote. I'd consider it the hands down winner in that department. Closest second is the C27 Horn, but it looses "degree of difficulty" points for not having incorporate a hole.
Ugliest is a bit harder, since I can think of two distinct types of "ugly". First those knives that just look weird. Gunting would be my prime candidate there, as it looks odd both open and closed. The other category would be an otherwise decent looking knife ruined by some specific feature which could just as easily have been omitted. The gross looking shell inlays that disfigured the black G10 Natives would make them my choice in that group.