Killer Prime

135L or 85L would be my pick in your case

and what about canon 100mm L and sigma 50mm ?
You would have a walkaround lens, a macro lens and a portrait lens...

85L or 50L would be my choices...

Another vote for the 35mm. I like that focal range on the 5D2 because I can focus close and get a lot of the background around my subject. I found it more interesting to use than the 50mm. I also found zone focusing with a 35mm to be a lot easier than with the 50mm (i.e., f/8 with manual focus set to around 17 ft), aiding in street photography.

85L is quite nice, but, it is a telephoto and you may have problems framing if you shoot up close (works better at a distance). If you don't plan on shooting it wide open to blow out the background all the time, the 85/1.8 is a good economical choice, especially given it also has faster focus. You already have a 100/2 which might be good enough.

If you haven't bought one already, I recommend getting a Eg-S manual focus screen. Works great with primes.

Add my vote for the 135 as well.

hey! I can relate, I'm studying for the fall semester in Florence. Been here for about a month almost. I only brought my 17-40, 35, and 85. To tell you the truth, the 17-40 and 85 get most of the loving. Sometimes I wish I even had the 135 for a bit more reach/background compression. I say bring your 24-70 and get either the 85L or 135L.

I started with 135L then got 35L a few months later and now also a 85L II.
They are all great primes and imo are the lenses every serious hobbyist should save up for

35L is fantastic as a walk around prime. Not only is it a great focal lenth the 35L is super sharp throughout its apeture range.

Actually the 100 2.8 non L is a killer lens, especially for portraits and about half the price of the L. Combine that with the 35 or 50 and you would have a versatile kit.

hmmm, I'm going to have to do some thinking. I think I might sell a couple to fund a sigma 85 1.4, and for some reason I'm leaning towards a 35 1.4. I'm wondering whether or not to keep the 24-70 though, I'd need some sort of wide angle replacement though, which is a whole new problem.