Sam the Ginormitron
Referring to Sam (or, on some occasions, Jared Padalecki) as a “ginormitron” was coined by Television Without Pity recapper Demian in his recap for 2.07 The Usual Suspects (source). At the time, it was a play on the sheer size of Jared Padalecki in comparison to Linda Blair during the scene where Blair's character questions Sam. Sam has also been referred to as “Darling Sammy” and “Captain Sincerity”, among other titles.
In the episode 4.20 The Rapture, Dean refers to Sam as "ginormo"