I don't really have one in terms of design. Playing only online I use the plain red, blue, green and black cards with white numbers/letters to help me see what's happening faster.
This thread got me googling stuff though, such as the differences between the designs of the kings, queens, and jacks. I had no idea the kings are said to represent Charlemagne (hearts), David (spades), Julius Caesar (diamonds), and Alexander the Great (clubs). The Queens and Jacks represent people/characters too. Interesting stuff.
If I ever win a big tournament the river card on the final hand becomes my default favourite.