Just like in Word Fu, you're given a selection of letters (this time a standard grid rather than cubes) and you have to make as many words out of them as you can in a few minutes. It lacks the power-ups of Word Fu, which robs a little bit of excitement, but it also makes you feel like you only have yourself to blame for low scores.
The big selling point of Word Scramble is its multiplayer. If you choose, you can play at the same time as 100+ strangers, everyone working with the same letter set. As the game progresses, the names and faces (or occasionally cats) of the top three scorers appear at the bottom of the screen.
I'm not quite sure why this makes the game so addictive, but it's undeniable that there's something about seeing the same grinning, cat-holding doofus at the bottom of the screen that makes you want to learn every word ever just to knock them off.
It's odd, but I think the reason I'm so drawn to Word Scramble is its ability to show me that, despite how I make my living, I'm right in the middle of the pack intellectually. How often can you get a reality check like that for free?
Scramble (Free, Zynga):