I don't think there's one pre-cut that's more useful than another. It all depends on
what pattern you will be using it for and how big your project will be. I suggest
choosing your pattern before buying pre-cuts. I don't know how many times I
bought jelly rolls then find I should have bought (let's say) 1 jelly roll and 1 layer
cake instead of 2 jelly rolls. They are not always interchangeable. So, choose
your pattern first then you can make a wiser decision on buying pre-cuts.
There are lots of free patterns at modabakeshop.com for pre-cuts.
I also like the books from Pam and Nicky Lintott. Check on Amazon.
I don't think I have a favorite pattern...too many to choose from. LOL