Best looking?
I don't think anyone has metioned the B-58. With four big engines hanging in the breeze, and the huge delta wing, this thing looks fast sitting still.
Unlike the XB-70, this supersonic bomber was actually used in service.
Like the XB-70, (which also looks as fast as it was) you can see one today at the museum located on the grounds of Wright-Patterson AFB, along with a huge number of other aircraft.
Special mention goes to another airplane that you can view at the same location as above (which I don't think anyone else has mentioned), the Me-262. Love the big engines on the little wing, as well as the slightly triangular section of the body.