Since you already have a 105 mm lens the next logical lens would be something 200 mm or longer. You have already covered the range from normal to 105 mm so why be redundant. If you are interested in wildlife photography a non-invasive 500 mm mirror lens would be a good choice.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.
135 and 200 are my favorite long lenses for 35mm format. 135 is one third of my basic three lens kit (along with 28 and 50). However, I love a 200mm lens, and I am not sure if I would have both a 135 and a 105. Think of it this way: Quarter your focusing screen with the 105 on. Imagine that just one of the quarters fills the entire focusing screen. That is about.what you get with a 200. It is great for all sorts of things, and is not heavy or large like a 300 or 400. If there is an AF Nikon 200mm f/4, that is what I would suggest.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
In 35mm, the only lens I have and use that is longer than my 85mm lens is the Zuiko 75-150mm zoom. I don't use it much, but the 150mm focal length has it's uses.
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
For the film cameras, most often I use either the 100-105mm (Minolta or Nikon) or the 200mm. I do have 135mm lenses also, including an f/2.0, but those do not see very much use. As Steve (Sirius Glass) mentioned, the 135mm focal length is not that different from the 100-105mm focal length, but there are times when the 135mm does provide the desired image size from that camera position. Often I will change lenses like using a zoom control.
The short telephoto lenses, such as 85mm, are used mainly for portrait work and when that focal length provides the image size desired on the negative from that location.
Ralph Javins, Latte Land, Washington
When they ask you; "How many Mega Pixels you got in your camera?"
just tell them; "I use activated silver bromide crystals tor my image storage media."
North America just north of that sharp right turn North America makes on the Atlantic coast.
I have a Tamron 28-200 that is always on one of my Nikon bodies at all times, I don't even know where the rear cover for it is any longer, I find it that useful. I really want to replace the Tamron lens with the Nikkor 55-200 but I lack the motivation right now, and the Tamron is doing a great job for me..
"Would you like it if someone that painted in oils told you that you were not making portraits because you were using a camera?"
"Shouldn't it be more about the joy of producing and viewing the photo than what you paid for the camera?"
I use a Nikon 50-135mm 3.5 lens a lot, because it is a great lens. However, in your shoes, I would also consider getting either a 200mm 4.0 lens (great value for the usual market price) or a 180mm 2.8 of AI or later vintage.