Everything, too! I have hoards of seeds from trading with other traders; just like to see those seeds germinate and flourish.
This year I'm proud to say is the pentapetes (thanks poisondartfrog); both the pink and red bloomed and I just collected seeds.
But one that still have me baffled is the canary bird vine - these never germinated no matter how I tried. Now I'm on the search for more seeds.