Gifs can also be copied straight from the site. Like if you search Google for example for a gif in particular, click the link, then while holding your finger down on the actual gif, copy it, then post the link, but make sure you add at the beginning of the link, and [/IMG*] at the end of the link. (Minus the asterisk).
It doesn't always work though, so be warned.
[img]http://gifs.gifbin.com/112012/1354558678_paintball_william_tell_shot.gif