I've tried ping pong balls and bobbers... my fish usually check them out but they don't hold the fish's attention...
I've also used those plastic eggs that silly putty comes in... poked a few holes in it and put frozen food in it... As the fish aggitates the egg, tiny bits of frozen food comes out. Usually not enough to bother eating, but the fish tastes the food and gets eager...
I picked up a motorized squid about 8" long... dropped it in my 300 gal 6' round Rubbermaid... it cruized around the perimeter of the tank for a few laps until it got stuck on decor... all the fish hid while this was happening... I only did it a couple of times.