I love making toppers for all my games and here is my most recent one I made for Roadshow. It is tied into the game play when you get flying rocks, shoot the right ramp when the bridge is out and of course starting multiball or jackpot via Ted's mouth.
Full details on how I wired everything up with pictures can be seen here:
When I had a TOTAN I made that $300 interactive sword topper from PDI for around $20 worth of parts. The lights are tied into the jewels you collect during the game play.
Full details on how I made this can be found here as well:
My GNR from a few years ago didn't come with one so I made one for under $10 that I simply tied into some flashers in the backbox.