#2 JBL and Kane
Both JBL and Kane are former WWE Champions. They have had some amazing matches and outstanding records in the WWE. While Kane had an unorthodox style of wrestling, JBL believed in using underhand tactics to win matches. The sad part about them is, despite competing in the WWE for so long, they were never made to compete against one another.
Both JBL and Kane were highly underrated, and, a match between these two superstars would have been an outstanding booking. WWE could have explored many possible story-lines to their rivalry. They could have sold arenas, and headlined several PPVs.
The only face-off which took place between these two wrestlers was a fatal four-way match also including John Cena and Batista for the number contender at the Great American Bash PPV for the World Heavyweight title. At present, this match seems a distant reality with meagre chances to occur.