Hacksaw Jim Duggan was "the first Royal Rumble winner", but it meant absolutely nothing for him. Even as a historical footnote, it doesn't mean that much, as technically the first Rumble match occurred in October 1987 with One Man Gang as the victor (it took place on a random, poorly-drawing house show). Furthermore, Duggan's victory didn't go down on pay-per-view, and the match only featured twenty entrants. Even worse, it only went thirty three minutes, and it wasn't the show-closing main event of the show. In terms of what he got for winning the bout, the answer is: absolutely nothing. The WrestleMania title shot for the Rumble winner was a gimmick that only started in 1993, so Hacksaw just had his pride and little else. So with all of that considered, Duggan's victory has to be considered a hollow one. What he won was more like an experimental battle royal, with the booking logic being that he was a big guy and hence a believable winner.
