Here's what interests me:
Canna: of course! You know I love the variegated foliage. Any and all sizes.
Dahlia: I don't have any of these currently, would love to see the huge ones as well as the two-tone type where they are darker in the middle etc.
Iris: anything unusual and I specifically like the dwarf type, would love to see some different colors of those.
Hardy Geranium: I specifically want: G. platyanthum and G. macrorrhizum but would love to see other offers
Tree Peony: would love to see purple, multicolor, yellow. Really anything, I don't have any of these either.
Clematis: I would love to see some oddities as the mainstream ones are traded pretty regularly. Like bell shaped, bi-color, doubles, red, yellow, silver colors... Some suggestions would be:
Jackmanii Rubra
John Warren
Alpina Frankie
Alpina Pink Flamingo
Belle of Woking
Perrins Pride
Lilies: I'm a nut for bulbs and I am just drooling over 'Royal Sunset'. For the right price I would definitely be game for these. Most lilies are easy growers and I think they would do really well since they're a sure bet even down in the colder zones.