What's a good example for class inheritance?

I'm writing documentation for an object-oriented language, and I wonder what kind of classes would be a good example for inheritance.

Some common examples:

class Person {
}
class Employee extends Person {
}

Currently my favorite, but I don't like Person->Employee because 'Employee' does not exactly look like fun.

class Bicycle {
}
class MountainBike extends Bicycle {
}

I found this in some Java tutorial, but it's not really obvious what attributes a bike should have.

class Animal {
}
class Bird extends Animal {
}

Same as the bicycle.

class A {
}
class B extends A {
}

Too abstract. The main problem is that such a class will need even more abstract attributes and methods.

Does anyone have a better example for a simple class hierarchy?