Favorite sail is probably Neil Pryde Zone 5.3 2001 model especially when used with my 80L wave board. Sweet handling and plenty of wind range. Love it. Still in use.
2nd favorite would be 4.7 NP Zone same vintage. Only used on windy weekends. Perfect condition.
3rd is my 6.5 NP V8 2008 model.
Used to have North Slalom 6.5 late '80s sail and it was very good too. Durable and powerful but a bit heavy. Traded this in on some Gaastra Slalom Sails in the early to mid '90s and they were good as well. Lighter than the North but still very nice. Kept these till mid 2000's when I changed all my slalom sails to NP. I like them.
Worst by far was a De Vries 5.7 wave sail I had in mid-late '80s which looked colourful but sailed poorly. Got rid of it and the Ten Cate Leaper board with a boom, mast, base etc to a bloke for $200. I made a loss on the deal but was glad to get rid of it; he thought he got a bargain.