Acetylene (ethyne) is perhaps the most interesting example.  With a triple bond between carbons, there must be two orthogonal π-bonds.  These are pretty easy to find as the MOs have the same energies.  (Note:  the molecule always comes up looking head-on down the molecular axis.)

Click on the 4th-7th MOs to highlight the π bonding & antibonding interactions. Other MOs are all in the σ framew ork--sp AOs on carbon, 1s AOs on H.