James T. Kirk (alternates)

Throughout the history of the universe, there have been multiple timelines, alternate realities and parallel universes that have all contained versions of James T. Kirk, as well as various clones and replicants.

Klingon James T. Kirk
In the quantum rift, a reality in which James T. Kirk was a Klingon briefly intersected with the reality of the Enterprise. 

Duplicates
A copy of kirk was made when the android duplicate of Roger Korby made one of him when kirk refused to do what he asked.

Another Kirk was created from transporter malfunction. This Kirk was seen as an evil and alter ego of kirk.