With Taunt, Klefki could Taunt other Taunter's before they Taunt, making it much harder to stop from doing its job. The other buff is giving it Stealth Rock. A big issue with Klefki is that it faces tremendous competition from both Deoxys forms. With Stealth Rock, it can do almost anything lead Deoxys would do, and could live hits much longer than Deo-S and be "faster" than Deo-D.
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Mowtom
Jacks0n
Another great buff to klefki would be some form of recovery, but I am not sure about flavour.