Most of us are, slowly but surely, getting rid of old incandescent bulbs and replacing them with LEDs and CFLs. If you have a few of those old bulbs lying around still and need a use for them, Instructables user ShakeTheFuture has a bunch of ways to repurpose them beyond throwing them away.
The video above tells the tale, but all of the five different light bulb projects in the guide start with carefully opening the bulb and hollowing it out so you can use it as a vessel for something else. The process is actually much easier than you might think, considering how fragile light bulbs can be, but once you have your bulb hollowed out from the bottom, it's ready to be filled with other things.
If you don't want to do anything after hollowing it out, ShakeTheFuture suggests using it as a fun desk accessory, holding paper clips - the weight of the clips will hold the bulb down, and when you need one you can just shake it out. If you're willing to get more daring, blue a washer with high-temperature sealant to the top, fill it with lamp oil (a paraffin base will work well) and insert a wick, and you have a light bulb oil lamp that you can refill whenever you like. You can even attach a solar garden light LED to the base and turn it into a solar lamp.
The ultimate though is to hollow out your bulb, fill it with mouldable plastic pellets, and toss it into the oven. When the instamorph/polymorph pellets melt, take the bulb out of the oven, add more until it's full and keep repeating the process. When it's completely filled with melted pellets, insert a corkscrew worm and then let it cool. Crack off the glass of the bulb and you'll have a bulb-shaped corkscrew. Hit the link below for walkthroughs on all of this.
5 Things You Can Make From Light Bulbs [Instructables]