The Studio Display that was on my old G4 tower has a history of being flaky. It was known for having a capacitor problem that made it 'pop' while you were using it. Well, it did that for a while when I had it, and I had it fixed once for it (outside of warranty, but Apple still paid). It stopped doing this after then.
So a couple of years ago I got a new iBook and gave the G4 to my mother who had a crappy little thing of a computer at the time (a Performa 6116CD; the other computer I gave her). She's been using it ever since. Until the monitor started popping again and popped its final pop three days ago.
So, I pushed a bit and got her to buy an eMac on my employee family discount ($800 evenish) and return the G4 carcass to me for resurrection. So, instead of using cash to buy a Mac mini like I wanted, I can just upgrade the hell out of the G4 and use it as a home media server. 
Now, of course, a G4/450 can't do video so well these days so it'll mainly feed the TiVo and my iBook some music and files, but, eventually, it will have a G5 big brother to do the video work.