My favorite lie is:

• The check is in the mail
• Wasn't me!
• I've never met that person before in my life! (or "Just a friend/co-worker")
• No, Officer. (or the very popular: "Two beers")
• No, that doesn't make you look (fat|stupid).
• I know that!
• It's not the size... (also, "That's alright; it happens to lots of guys")
• Your call is very important to us...
• But PerlMonks is work related.