Is there an app other than Witch that allows windows switching (not app switching) with cmd+tab? I found the Witch app (http://manytricks.com/witch/). Are there any other solutions?
Contexts looks nice, but I've never used it personally.  It seems to be similar in functionality with Witch, but it has a more modern (iOS 7-style) design.

It does have the ability to map itself to Command+Tab.

It costs $9.