Need to find that one emoji for iMessage or just about any other app? Don’t know the name of your favorites? You can trigger the emoji panel with ⌃-⌘-Space (Control-Command-Space), then start typing the name of the character(s) you need. Arrow around and press Return to use the selected character.
Mouseover any emoji to see its name in a tooltip.
Finally, if you have the old-style emoji panel that’s a floating window, click the layout icon in its upper right to get the new, spiffier, more iOS-like popover panel pictured in this post.