My main character, Alma, in Gods Are Watching was originally to be called Alm. Switching her gender from male to female was the last major change I made before beginning the story, and one that I've never regretted. (Plus, the name change was easy: I just had to tack on an 'a'.)
The deuteragonist, Calvin, was almost called Klein. I thought that 'Klein' sounded too annoying for the second protagonist (no offense to those with the name!), and plus, I wanted another name with two syllables so that he could have a sense of resonance with Alma to make up for their contrasting personalities.