Font icons
Use of icons has become more prevalent with mobile and app design; alongside progressive disclosure and audience overlap (both in regards to age and language)
Creating icons successfully is very skillful (having variations for different sizes being a subtle in itself). Using them in projects and wanting to change colours normally means taking them (or the sprite) into an editor—fiddly at best.
But with icon fonts, we have no problems with http requests and you can change size/colour simply via the css. It also deals with the problem of supporting high density screens
The above example (with just font-size and color attributes changed) is using the Font Awesome, which makes application a breeze. No more images—even for social icons! (love the github icon—won me over)
There are great other resources out there—but looking forward to putting some time aside to create my own!