When creating applications, I predominately use 'Classes' (sometimes, where appropriate, 'Structures') to model real life problems. However, to set things straight, it is important for everyone to realize that the .Net Framework offers 6 (5 in C#) types to build custom types.
They are in random order; Class, Structure, Enumeration (Enum), Delegate, Interface and Module (not available in C#). All of which, except for the 'Interface', inherit from the Object data type, which is the root type of all types in .Net.
Just a thought for you developers out there.