2. Rey Mysterio
Rey Mysterio is regarded as the greatest high-flyer and little man in WWE history. Rey Mysterio is a three-time world champion, former Intercontinental and tag-team champion. Mysterio is also a Triple Crown Champion and won the Royal Rumble in 2006. Despite all that he has accomplished, it's extremely difficult to fathom that he hasn't competed inside Hell in A Cell.
Like the afore-mentioned Jeff Hardy, Rey Mysterio is known for taking dangerous risks inside the ring. Mysterio could easily put on a brutal match of the year candidate with anyone inside the Hell in A Cell.
Mysterio has been inked for a return to the WWE, where he would like to cap his career off. However, as great it would be to see Mysterio compete inside the cell, it's unlikely that WWE would put him inside the cell given his age and past injuries.