Thats a hard one.
but a few jump to mind immediately.
Skipley Bonanza has been producing steadily, and I keep being amazed at how beautiful it is. I had it last year, but it bloomed late and I only had 2-3 blooms all year. This year it has been blooming for months.
Enchantress has me enchanted
Spartacus - usually I odnt get many blooms off the big ones, but Spartacus has been putting them out.
Galen Rose - I added quite a few new Ball dahlias this year, and this is probably my favorite of them
Zapf's Desert Storm has also been consistently beautiful
If you asked me next week They might be different, but these are the first ones that came to mind.