A euphemism for penis or dick. Along with being a slight dig at whoever it's used against thanks to the connotations of baloney (cheap, unwanted, undesirable, etc.).
Saying this will also immediately make you friends with any and all weebs who've watched Neon Genesis Evangelion since that's where this phrase originates from (the ADV Dub of the series from 1997 to be exact) to the best of my knowledge. Thank you, Amanda Winn Lee (ADR Script Writer and Voice Actress for Rei Ayanami) for writing and saying this!
Rei: Woaagh! You're the jerk who was staring at my panties!
Asuka: Hey, what do you mean by that?! You're the one who was flashin' them y'know!
Rei: Oh and who are you and why are you defending him? Are you riding his Baloney Pony?
*shock envelopes the classroom*
Asuka: We're just really good childhood friends! You shut up!
Hikari: Be quiet you two! We're in a class, not a bar!
Misato: Hey, this is more entertaining than class! Go on, I want to see how this turns out.
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 $2million.