Is there a way to easily access the emoticons I use most in iMessage?
When you add the Emoji-keyboard on iOS (Settings &gt; General &gt; Keyboard &gt; Keyboards &gt; Add New Keyboard &gt; Emoji), it automatically collects the recently used emoticons on the first tab at the bottom (the clock icon).

The same goes for Messages.app on OS X; when you open the Emoji-selection from the smiley-face in the input box, it shows the recent ones first.

However, on OS X you can select which emoticons are shown in the favourites, a feature currently missing on iOS. You can do this by opening the Characters viewer from the top right corner of the Emoji-popup and selecting Add to Favorites for the emoticons you like.

Also, there is no way to sync these usages and selections between devices, at least currently and using stock OS's.