1) Prase used whilst moving one's eyes from side to side in a shifty fashion, often to indicate the phrase beforehand was a lie or meant sarcastically.
2) Based upon the shortcut for an MSN emoticon.
"James you're very good at guitar... Shifty1"
"Nat doesn't drink or smoke! Shifty1"
MD: "Did you rape my Papus??"
Charlie: "No of course not! Shifty1..."