These 1/2 price ticket booths are all over the strip, with nine locations from New York-New York on the south end to Circus Circus on the north end.  Very helpful staff is there to answer questions and provide information about the variety of shows that are for sale.  While they can't recommend a specific show, they are a font of knowledge and you can pump them with questions to get a good idea of the shows they think are the best.  Don't even think about grabbing a show in Vegas without hitting the Tix4Tonight booth first.  For $2-3 they also sell discounts for restaurants around the strip, some offering 50% off the price of an entree for everyone in the party.  Check it out.