I'm in search of a unique lense for my Nikon D3100 digital camera?
I'm bored with the lense I have, cool lenses?
Bored?
Maybe photography is not for you.
Back in the day, we used a single 35 mm camera and a 50 mm lens and spent years learning how to use them.
If you need to add another lens to your system, you need to figure out what subjects you will be shooting.
I love my 300 mm f/2.8 and 14-24 mm wide angle zoom, but they may not be what you need or want.
Here is a list of all the Nikkor lenses made and another that shows what each focal length "sees"
The lens won't help you make exciting images unless you go to a $1000+ pro grade lens. Even that won't do much unless you understand how to use such a beast. A simple thing is making aperture shapes. Just in time for Christmas! You can cut out little reindeer, santas, snowflakes, and elves.
http://www.iheartfaces.com/2011/12/shaped-bokeh-tutorial/
You're limited only by your imagination.
Try macro. It is fascinating and opens up a whole different perspective on the environment around you. And it can be technically challenging, which makes you learn/enforces your knowledge on the fundamentals of photography.
You should not become bored with macro for quite awhile.
Money no object I would get a 200 mmm 2.0