Lion (AKA RAWR I'M A LION!)
A white circle with a right side up >:3 in it and a speech bubble with the caption "RAWR I'M A LION!." Lion showed up in early 2006 with the lion image and it went with the saying "JESUS CHRIST IT'S A LION GET IN THE CAR!" and the very first thread was very popular among /b/ with many shops of the lion face on 4chan memes, lion pictures, and other stuff. Lion was posted many more times in the following months and eventually lion and JESUS CHRIST IT'S A LION GET IN THE CAR! became a part of /b/ and you'll never look at a lion or >:3 the same way ever again.
The meme has had slight crossover to /a/ referencing Fate Stay Night and pictures of Saber with lions.