Ianna

If you want something big and impressive, Pampas Grass will do fine in shade, but it is a slow grower here. You often need to buy a big pot to get the big clump.

As a suggestion, since I see you are in Montreal, go to the Botanical Gardens (in a month or two). They have an ornamental grass section and you can see what you like the look of and give it a try. They will also have a garden and plant sale there the weekend of May 25th, and you will almost certainly be able to buy some nice grasses.

BP

What is sold in nurseries in Canada and called Hardy Pampas Grass is actually "Erianthus ravennae" or Ravennae Grass. It is hardy to zone 5 (-20*F), grows 10-14' high and is an extremely hardy native prairie grass. The gray-green foliage turns bronze in the fall and the plumes are creamy white, with stems that are strong enough to provide excellent winter interest.

I have a clump of Ravennae grass in my garden that started as a tiny plant in a 3" pot and over the last 6 years has become about 3' in diameter at the base and is a spectacular 10' tall. It is very late in coming up every year, showing green finally around the end of May, beginning of June but then grows quickly.

For your shady conditions, you could consider growing Hakonechloa macra 'Aureola' or Japanese Forest Grass. It forms stunning cascading clumps of green and gold variegated foliage, about 14" high. It will grow in full shade but the variegation is best in part shade, bright shade or locations where it will get morning sun.