Categorize the contents of content type without creating a different template file for each I want to apply similar style to the nodes of same content type (style may vary or may be same between content types,  but will definitely be same for the nodes of same content types) without creating a template file for each of the content type.

I know one way is to create a template file as node-TYPE.tpl.php but I am looking if there is some other way.
You can use

Panels Module 

It gives you UI to override node templates,providing appropriate selection criteria you can have different layout as per content types.

Display Suite

Display Suite allows you to take full control over how your content is displayed using a drag and drop interface. Arrange your nodes, views, comments, user data etc. the way you want without having to work your way through dozens of template files. A predefined list of layouts (D7 only) is available for even more drag and drop fun!