William Castle was a man who created gimmicks to bring people to see his B-movies. From skeletons flying overhead to the Coward's Corner, Castle knew how to fill those seats. Here's a trailer for a documentary about him.
His best known gimmick was for The Tingler, where selected seats were literally electrified. Here's the trailer for that.
If you've got the time, you should really read this salute by John Waters, from his book Crackpot. Among other things, it tells about the time a mischievous film projectionist made use of the electrified seats from The Tingler during a screening of The Nun's Story.