For me it would be these three that justify being given the title of 'Unforgettable Royal Rumble Winner'
Lex Luger - Well he was a joint winner, went on to have a dull title match at WMX and then never did anything of note afterwards in the WWF.
The Rock - Did he win? Joking but it was hardly a career highlight that he is remembered for, more people would remember his 'This is Your Life' segment or 'The Rock Concert(s)'. Also the fact his title match at Mania was made into a fourway and he didn't walk away with the title.
Sheamus - It was a forgettable Rumble match to be honest, from 12 months ago I remember more of the WWE title match between Punk and Ziggler and it wasn't until the other day that I remembered that Jericho was the man he threw over the top rope to win it. His title match at Mania was a silly waste of himself and Daniel Bryan and opened the show at least the year before it was a decent contest for the WHC.
On the next tier in terms of forgettable Rumble winners for me it would be Big John Studd (but that was a WWF career highlight for him), Stone Cold '97 (but then it was a classic finishing sequence and his performance on the night was fantastic) and Vince McMahon (but that was the part of something big w/Austin and we are reminded about it through the likes of Lawler, Cole and Ross to this day so we can hardly forget about it).