I use LICEcap fairly extensively when answering questions on Stack Exchange - its a VERY intuitive tool for making gif-based screen captures
You open the application, select an area to record, choose a filename to save it, and do your thing so it can record.
However, this is Windows and OS X only - I've occasionally toyed with using a Linux VM and capturing the VM window, but I'd like a native alternative that would record a gif the same way.
What could I use?