I don't grow a lot of diploids these are all good garden plants with sturdy scapes and provide many blooms during the bloom season.
A few doubles....
Condilla, already mentioned but I am in need of some color tonight so will post an image anyhow!
Mount Helena, a favorite, well branched, always doubles for me.
Roswitha, great plant with pretty blooms.
Unusual Forms....
Vanilla Gorilla, tall (44" registered height) extra large yellow-cream UF with super plant.
Itsy Bitsy Spider, early bloomer, cute tiny blooms.
Fitzasaurus, 9" red with strong tall scapes, grows much taller than registered height of 32" here. Closer to 48".
Spider....
Magic of Oz, , pleasing combination of yellow/cream/pink with a rose eye and a large green throat.