I'm a fan of westerns. But it always made me sad that the loner could never break from their archetype and find their own love or a purpose in life. The riding off into the sunset always bothered me. Why couldn't they stay and make a life for themselves? Loners tend to be male so an easy way to refresh this archetype is to try a female character but please oh please don't blend them with a battleaxe character as you get the female warrior who doesn't talk to anyone, all mysterious.
Loners that are done well:
Most of the ones I've seen done well have actually come from movies and the like but I thought I would start with the one in a book that I think is done to perfection. Siccarius is an assassin who ends up being humanised by a woman who loses everything important to her. The slow burn is what makes this work so well. The author Lindsay Buroker doesn't just have him change over night. In fact, out of all the characters he changes the least. We only know there is a change at all because of small glimpses into what he is feeling.
So to get a loner right you can't change them too much or too fast. The westerns knew this and they never have enough time to explore the possibilities. In a series you really can see how a loner can finally create connections.
Gross Point Blank does something similar and again they do a second chance trope to show the change happens over a long time.
Dragon Ball Z
Talking about using time to show change Goku and Vageta are good examples of the loner. This is a good series to look at the archetype as they are two different types of loner. Goku is a loner/ingenue and Vegeta is a loner/rogue. Both eventually find those connections and get the life they deserve. If you look at Goku he never loses his need for distance from the masses. He likes to go to the wilds often.
They've kept it fresh by blending it with other archetypes. Otherwise the archetype could be flat and used only to move the plot forward without being a character of depth.
Loners can be interesting as they never see themselves as victims but rather are willing to alienate themselves from others in order to do the right thing.
So far the examples of good loners have been those that are violent but there are also great examples of ones who embody more of the ingenue archetype as well. I said before that putting this trope on a woman often works but also taking an archetype from what is traditionally a female role and putting it onto the loner can work as well.
Wall-E though demonstrates early in the movie that he wants a connection. While many loner characters avoid connections. The situation has made him a loner rather than his personality. This makes his change to something so different from other loners is believable. If you are going to use the loner archetype consider isolating them through circumstances rather than personality.