Ideas for creative portrait lenses?

I've been looking at getting a new lens and have really been enjoying a lot of portraiture. Realising this is the main style I would like to pursue, I thought a lens that would be suitable for this would be best, however, I wasn't just looking for an average lens as I've already got a fairly decent one, I was thinking about some slightly more creative ones I suppose. I started thinking about this when I saw some of the lensbaby products which seemed to have a really nice effect for portraits and macro photography etc but I've heard mixed opinions when looking into it. Does anyone have any suggestions of a nice and quite versatile lens for a Nikon DSLR? I'm not totally sure what I'm after so far so I'm open to suggestions.

Here are the recommended lenses for Nikon digital SLR

* DX portrait lenses for cropped sensor cameras:
> 50 mm f/1.8
> 60 mm f/2.8 macro
* FX portrait lenses for full frame sensored cameras
> 85 mm f/1.8
> 105 mm f/2.0
> 105 mm macro f/2.8

The macro lenses will give you a secondary use for those portrait lenses.

Some photographers who need a 70-200 mm f/2.8 for shooting sports, use that lens when shooting portraits. After you visit the Nikon website and see what each lens costs, you can pick the lens which best fits your current budget

Since you mentioned interesting/creative effects, have you tried looking into vintage lenses? These lenses can provide soft contrast that works well with portraits, and some also create really organic looking effects like flares or bokeh distortion effects.

You would be best to buy a prime lens ie not a zoom one to get sharper images and a 50mm one would be ideal for portraits. http://www.popphoto.com/gear/2011/04/round-which-nikon-50mm-lens-should-i-buy