My favorite is February Silver. It is a very early bloomer - blooms a week after tete a tete which is very early. The blooms last for a long time. This year the blooms last about 3 weeks. The flowers fade very gracefully such that you don't even notice it.
3/21
4/11 - 22 days after the above pic was taken
4/11 close up
Love it so much that I ordered another set from Van Engelen this year.
Another nice one is Geranium. It blooms like crazy and an excellent increaser.
Fragrant Rose is another nice one that is very fragrant and very pretty. I am not sure if it is still available.
Another pink one that I like is Perfect Lady. Unfortunately this one is not a robust one and they don't return as well as the others noted above. The flowers are so beautiful though!