Twislim attempts to fit your height/weight combination on a scale by comparing with measures from the rest of the twitosphere.
The image below shows an example. So as described on the website, “Are You a Colibri or an Emu Bird?”

Oh My Science is a fun application that searches the public timeline for tweets with the word 'god' and replaces...
LOLWRUS is a mashup that combines a tweet, turns it into LOLSPEAK, and combines with a picture of a cat...