A person who you don't normally associate with except for on weekends. Also a person who you don't normally associate with unless they have something to offer.
Girl #1: "I don't have any money for the bar this weekend..."
Girl #2 "OH! Call up your weekend friend, she'll foot the bill!"
Girl #1: "Good idea!"
A Shackteau is a humble, weather-beaten, structurally questionable shelter located in a spectacular or highly coveted place—Wales, Jackson Hole, Sun Valley, Crested Butte, coastal Maine, the Alps—where the building itself may be worth almost nothing, but the dirt, view, access, and mythology make it absurdly valuable.
In use:
Shackteâu - We thought it was an abandoned shed until the realtor called it a rare alpine Shackteâu with unobstructed views and listed it for $2 million.