I couldn't possibly exclude the first-ever WWE Champion from this list.
After winning an imaginary wrestling tournament in Rio de Janeiro, Brazil, the original "Nature Boy" Buddy Rogers was crowned as the WWWF's first-ever champion. However, something that WWE often fails to mention is that Rogers' run was awfully short, clocking in at a mere 22 days. There are two reasons for this.
The first is that the 42-year-old Rogers suffered a heart attack not long after winning the title, and promoters Vince McMahon Sr. and Toots Mondt were too concerned with his well-being to allow him to continue wrestling extended matches. The second reason is that Rogers was a heel, and heels were generally not allowed to have lengthy title runs in the territory era - they would only ever win championships so that they could drop them to popular babyface wrestlers a couple weeks later.
As such, Rogers dropped the belt to Bruno Sammartino in a 48-second match at Madison Square Garden in May 1963. Though his reign was short and ended rather anticlimactically, he was the first champion, and no one can take that away from him.