Despite the strides taken with internet media, the ancient Graphics Interchange Format remains popular for presenting animated images, even with its 256-colour limitation and sub-optimal compression. GIF also does not support "buffering", so when you do view one, it often has stuttered playback or starts in the middle of the loop. Fortunately, Firefox and Chrome users don't have to put up with this.
Both browsers have an extension available to them called "Gif Delayer", which can be downloaded from either the Chrome Web Store or Mozilla's Add-on directory. Its purpose is simple — it prevents GIFs from playing until they've finished loading, saving you from having to wait for the animation to loop again or putting up with jerky frames.
It's not exactly like watching an FLV or SWF with playback controls, but it does solve the most frustrating aspects of viewing GIFs.