The 135L is great for street photography. It allows you to capture performers without getting too close, and blur out the background nicely.
I love using this lens at Disney World to capture the cast members doing their thing.
The 135 also does landscape quite well. Not all landscapes require a wide angle lens! I also like that you can take a landscape shot and still manage to blur out the background.
This lens excels at portraits. After all, this lens was made for portraits. It's tack sharp wide open. I use this about 95% of the time when photographing kids, because you can just step back and let them be kids!
Short range wildlife? It's got that covered too! Okay, so normally you wouldn't want to get close enough to two wolves to fill the frame with your 135, but I took this at the Adirondack Wildlife Refuge, where you can take a walk with the wolves.
This lens is a boon for short-range sports. Living in Saratoga, many a morning are spent at the Oklahoma Track photographing the horses exercising or at the main track taking photos of all the action. I swap it between my 6D (when I can get closer) and my 60D (for when I need a little extra reach).
Although not an ideal length for polo (a zoom would probably be best here), I did come away from a polo match with some keepers.
The main thing I love about this lens is its ability to blur out the background. There are a number of lenses that do this quite well, but this paired with the size, reasonable price (compared with other "L" lenses), and focal length make it very appealing to me. If I could change one thing, I might wish it to focus a hair faster. When I used to shoot primarily crop sensor, I used Canon's, 100mm f/2 lens, a non-L lens, which focused a bit faster than this. That's not to say the 135 focuses slowly, just not as fast as I'd like for when I'm shooting action.
Do you own the 135L or have you ever shot with it? Do you love it as much as I do?
Tools I used to create the photos this post: Canon EOS 60D, Canon EOS 6D, Canon EF 135mm f/2.0L USM