I recently made a few 555 timer circuits successfully. The reason I say successfully is because I have never been able to get them working in the past. All because I had the pinout all wrong. Now that I got them working, they are really cool. The first one is a bi-color LED alternating between its two colors. The second one is supposed to be a "ticking bomb" sound but it sounds more like a heartbeat. That's it on 555 timers for now but I still have a couple more ideas so stay tuned.