For my experience, most pleasant taildraggers: DHC-2 Beaver, Cessna 180/185/170B/172TW/140, Piper PA12/18/J3, Found Expedition, Wilga. Less pleasant (you have to work at it/worry more: Maule, Harvard, Stearman, SM1019, and a the least forgiving; Thurston Teal. I have found that the Scout/Citabria and Decathlon are rather middle of the road, and thus good trainers. They will let you learn, and get a good lesson, without biting you too fast/hard.
That all said, some tailwheel flying skills will make any pilot a little better, and are well worth the effort!