Favourite Season Finale Cliffhanger!
This is easy.
Best of Both Worlds ended season 3 of TNG on an incredible note. Captain Picard had been captured and assimilated by the Borg. The Borg ship was on its way to earth, intent on wiping out humanity, and the crew of the Enterprise had one chance to stop them. Commander Riker gives the order to fire… And To be Continued appears. Pure television gold.