I got a sudden urge to gain some reputation on Stack Overflow and went looking for questions with a bounty when I found this particularly interesting one - Loosing hover when animating with jQuery (without moving mouse).
The author of the question had made a fiddle so there was no effort in trying to reproduce the problem which is often a time consuming business.
I made my own fork and started hacking away. After a while I came up with a solution and saved my fork. The solution might not be the prettiest you seen but what’s pretty is how jsFiddle worked as a playground that everyone can use with only a browser. Combined with Stack Overflow this is pretty powerful stuff for getting help from the community.
In the time of writing I haven’t got any feedback on my answer but I’m happy nevertheless for finding such a useful tool.