Well, when I was last in America, I decided I couldn't resist the amazingly cheaap prices compared to over here, and bought myself a Highway 1 Tele...I went back to the hotel and was playing with it happily and then realised I had no way to get it home...Panic set in
Right, so I head back to the shop and pick up a hard case. Then I phone the airline "I have fragile, oversized baggage, what can I do?" They told me basically to take it up to check in, and explain the situation. I did this and the person at check in did some phoning and whatever and was like "Right, well there's a locker that the flight attendants keep their stuff in - you can leave it in there"
So i kept it through the security checks and everything and took it up to the gate, and then when boarding I handed it to the person and they took it up near the back...Pressurised cabin and everything, win win situation :)
Only downside was that I had to wait 'til everyone else was off the plane before I could get it back