Sharpest Landscape lens?

I'm guessing that the Canon 17-40L will be the pick here, but I'd be interested to know what you think.

to be honest, most of the "good lenses' will do the same job for landscape since you mostly shoot off a tripod with a high F stop. to me, the important thing would be CA, colors etc..

USM-UnsharpMask...even can decide how much sharp u want.

Depends on how wide you want to get, but I agree the 17-40L or the 24-70L on a Tripod stopped down to f/8 or 11 will work great.

Well I have had some stunning landscapes from a Sigma 50-500. All my "L"s do a great job.

It depends what you want in focal length. Ultra Wide angles like the 10-22 EF-S aren't known to be a great traditional focal length for landscapes. Too much foreground, while making a mountain range a tiny after thought in a very distant horizon. It forces some creativity. Like getting a whole tree in frame while being really close to it.
A 17-40 will be a great starting lens even on a crop body. Like most lenses, stop down to about F8 for a sweet spot in sharpness. Most are sharp between F8 and F11. If sharpness is your idea, use a steady tripod. Use a remote and/or timer with mirror lockup. Even dedicated landscapers will include a telephoto to isolate a distant subject, like a faraway mountain top.

I've had some pretty sharp landscapes with my 300mm f/4L IS

Do you really need mirror lockup/cable release when you're shooting at 1/500 with a 17-40??

My 17-40 and 70-200 are a great landscape combo on my crop body, the latter being very useful for sunsets and mountains. On my last trip to Peru, Bolivia and Chile (which has the best landscapes in the world in my opinion) I din't need any other focal range.

I would love to have a 300 f2.8 or a 400 f4 and just make a huge panorama.