I managed to get out of a mid-routing segment once on AA by playing the confused young student card (it helps that I'm 25 but look about 19). I was flying SEA-ORD-MKE-STL-SEA, and it was much more convenient for me to get off the plane in ORD and meet my MKE-based friend there, as we were driving south to Louisville for the Kentucky Derby. Not to mention there was a 4hr layover in ORD before the flight for MKE left, so I was saving myself 4 hours of layover, plus flight time, plus the 1.5hr drive from MKE back down to ORD. When I priced out SEA-MKE-SEA, it ended up being $125US more than the via ORD routing, so I took my chances on the segment skipping.

Got to ORD, got off the plane, went to the ticket counter, made big nice doe eyes, and said "I will not be using the last segment of this ticket, as someone has come to pick me up here to save time. You may release my seat to another passenger." The ticket agent said, "You're not really supposed to do that, but it's OK. Don't do it anymore." I replied with a Yes, Sir! and went on my merry way.

As a side note, on the flight back the MKE-STL flight went mechanical, meaning I was going to miss my cnxn in STL and reach SEA late, thus missing the bus home to YVR. I explained all this to the AA gate agent, and she instantly had me put on a Midwest Express flight to Vegas (comfy biz class seats, good cookies!), and an AS flight from Vegas to SEA. I was VERY impressed by their ability to accomodate me with no fuss and no muss, on the most convenient airlines possible.