My Palm Tungsten T PDA. I use it all the time for both business and pleasure. It organizes my life, lets me keep informed and entertained with reading material, news, games and MP3s. IT's like having a computer in your pocket (oh, wait, it IS a computer in my pocket!).
My next favorite pocket item these days is a Victorinox Cybertool 29. It's been useful daily sisnce I added it to my EDC although I'm starting to think that with a Cybertool 34 I could quit carrying my Micra as I'd add scissors and would gain pliers as well in the exchange.
Anyone carry a Cybertool 34 in Khakis? How bulky is it?
Then of course there's the clipped EDC knife of the day and a small Surefire and the back-up Arc AAA.
How do you really expect someone to pick a single favorite???
jmx