OK so I've tried all of this and still my phone number is not listed in iMessage's preferences in Mountain Lion. Any suggestions?

Hi,

The Apple ID registered in the iMessages account on the Mac version of Messages is the same one you have entered on your iPhone ?

On the iPhone in Settings > Messages > Send and Receive the iPhone Number and Apple ID are ticked ?

Which of these is being used as the "Send New Messages from" ID ?

Have you restarted Messages on the Mac ?

Have you put the iPhone in Airplane Mode ?

Is Messages "On" on the iPhone ?

9:55 PM Friday; February 22, 2013

Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"

 iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images."  No, Seriously