The diamond formation isn't really a trick, but I felt it fell under the unusual category.
It is a formation with the QB in pistol with a HB behind him as well as a HB and a FB beside him. I love the read and triple options out of this formation because you get a lead blocker from the extra players in the backfield. It also has a neat double screen play. It is the playbooks of Arizona State, Clemson, FAU, Oklahoma State, Louisville, Missouri, TCU, Texas A&M, Tulsa, and probably others.