#2 Spike Dudley

Spike Dudley is best remembered by WWE fans as the third member of the Dudley Boyz and as a former Cruiserweight, European, Hardcore and Tag Team champion.
During his four-year spell in WWE, the pint-sized Dudley featured in just one Royal Rumble (2004), where he entered at #13 and was attacked during his entrance by Kane.
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The incident was similar to how Curtis Axel was ruled out of the 2015 Rumble and, though Spike still counted as an entrant, he was unable to compete and he was never officially eliminated from the match.
So, technically, as Spike never entered a Rumble match again, he is one of just four official entrants who has never been eliminated.