Two stories:
Bad:
One of my students on his first solo x-country could'nt touch down at a class D airport (they also like "play" big aiport over there) because they were painting the runway centerline on ONE of two runways and reached the intersection - surely nobody figured that that is a helicopter and could have touched down roundabout 5000 ft away from the workers! (student was to afraid to insist and did'nt land)
good Philly International, pick up a photographer. Tower asked me for my intentions and told me to keep my squawk... took a little longer than I thought, so I figured that I should call clearance first - bad weather somewhere, everybody got full clearances and after 2 min not even keying the mike I decided to give it a shot on the tower freq..
Of course the guy has changed and I told the new guy that his collegue told me to keep my squawk:
Tower: "That was'nt me, standby!"
Me: (

awaiting the "contact clearance") Roger
Tower: (worked five airliners and then) "Helicopter on the GA ramp, are u N-12ABC?"
Me: "Affirmative"
Tower: "Ok, I found a note here, you can proceed as requested!"
Me: "Roger Helicopter N-12ABC"
Tower: (cleared six or seven airliners) "Helicopter N-12ABC I'm not picking u up - you didn't take off yet?"
Me: "negative sir, I am waiting for takeoff clearance"
Tower: "I gave it to you already - proceed as requested!"