Following from the other thread, can we do the opposite? What are you really pleased with?
For me it is the blue perennial geranium that I planted (think it might have been Johnson's Blue, but can't quite remember). It has flowered and flowered and flowered. Also the Erysimum 'Bowles's Mauve which I grew from cuttings (my first attempt!)... which has also flowered endlessly.
I'm always looking for things that flower for ages ... so any suggestions gratefully received!