At my home airport, ATL, I would love to see some more international carriers. Currently we only have BA, AF, LH, Korean Air, South African, and Aeromexico. Considering that ATL is the busiest airport in the world, I think that's kind of pathetic. Almost everything that doesn't have some kind of partnership with Delta has been driven out. British Airways and Lufthansa are the only ones that still survive. It'd be great to see KLM back, Swiss in order to replace the former SR service to ATL, Austrian (never saw them here, but they did serve here), JAL (that was the first 747 I ever saw), plus any other foreign airlines that have been driven out. I'd also love to see some other Asian carriers, CSA, and Alitalia.
On another note, I'd love to see the Concorde in the air anywhere. I was at CDG over the summer and was just walking through the terminal looking at planes before my flight back to ATL. It was all 777s if I remember correctly until I got around the corner and it a terminal right next to ours was a Concorde. That made my week. I was just about jittery with excitement. I saw it taxi away, but I never saw it take off. Now I just want to see one flying (to be on it preferably, but I'll take just seeing it because if I ever fly the Concorde, it'll be out of someone elses wallet).