GIF Brewery, developed by Patrick Rogers, is my favorite app to create animated GIFs (with a hard G) on OS X. Every time I need to show an app's particular animation or effect, I mirror my iOS device's screen to my Mac with Reflector, capture a video, and turn a specific portion into a GIF.
The latest update, released last week, contains a new preference to automatically snap text overlays to horizontal center and, even better, settings to control fade-in/out times for overlays. These two minor additions make dealing with text overlays in GIF Brewery much easier, leading to better results.
GIF Brewery is $4.99 on the Mac App Store and I can't recommend it enough.