The most traditional "BBQ Guns" are SAAs and 1911s, but those aren't your only options. Pretty much any high-quality American-made (or designed) gun will do, especially larger-framed Colts and S&Ws, so long as it's been gussied up a bit with engraving (preferably on the metal and leather holster, but you could get by with nicely carved grips). Anyone who tells you that a Hi-Power is unsuitable should be disregarded.
As nice or interesting as something like a Mateba Auto-Revolver or a Desert Eagle might be, they're foreign and shouldn't properly be used as BBQ Guns.
Some will differ with me, but my personal opinion is that if you're strapped for cash then even something like a Taurus revolver which has been properly shined and is displayed in a classic and traditional manner is suitable (although obviously you want to move on up eventually).
If it has plastic on it, it's almost certainly unsuitable for this use (if nothing else, because it's probably a foreign gun). Again, though, if you're in a situation where you need a BBQ Gun, it's better to have a Glock or Sigma than nothing at all.