Why did Sylar let Mr. Bennet Live?

Sylar likes to play mind games. What would be more fun for him? Killing Mr. Bennet, or locking him up with the knowledge that he can do nothing to save his daughter? I'd imagine Sylar was sitting in that house, just thinking about Bennet locked in that cell, powerless, while he charmed Mrs Bennet and waited for Claire to come home. That was a huge thrill for him - that sense of power over the entire Bennet family.

He probably has a hidden purpose for not killing Mr.Bennet. He could've lost one of his enemies in that scene but he just locked him up. So maybe he needs Mr.Bennet to do something for him in the upcoming episodes. Let's just wait and see!:)

I agree with what's already been said, but I also wonder if Mr. Bennet doesn't have some kind of special ability of his own we don't quite know about.