Sure, I'll throw down with a personal favorite, a loophole that hasn't been closed.

If you 1. have to make a connecting flight on Southwest, and 2. will not be checking baggage, you can book your roundtrip online as two open-jaw roundtrips.

For example, Chicago-Little Rock-Tulsa-Little Rock-Chicago would become 1. Chicago-Little Rock-Tulsa and 2. Tulsa-Little Rock-Chicago.

Advantages:
- 8 RR credits for your trip (instead of 4), getting you halfway to a freebie
- on some routes, it may be cheaper

Disadvantages:
- on most routes, it costs more, but sometimes only by a few bucks (do the math!)
- checking baggage/missed connections become a nightmare

I've got more...