That's a good one, I actually don't recall how early he used the Tombstone, whether it was as early as his Survivor Series debut (so would be one of the Dream Team - Dusty/Hart Foundation/Koko), at Wrestlemania (Snuka), or what.
First thought was Wrestlemania, so will go with Snuka.
Second thought was Survivor Series, so if not Snuka then probably Koko B Ware or Bret (doubt Anvil or Dusty would've taken a piledriver). Can't actually visualise how the match panned out apart from Dusty & Undertaker being counted out.
Otherwise some random jobber like that guy that used to always wear the long silver/grey tights (remember him being against a bunch of people on the short WWF clips that used to show on "Mobil Sport", a variety sports show in NZ in the early 90s hosted by Clint Brown).
Speaking of the early Survivor Series events, I used to love looking at the teams in the WWF magazine from those years, as we didn't get the tapes till long after the magazine came out. Anyone else used to look at those team pics and imagine how the fights would pan out, back in the day?
