BASH is my favorite. It’s really a preferential kind of thing, where I love the syntax and it just "clicks" for me. The input/output redirection syntax (
1>, etc) is similar to C++ which makes it easier for me to recognize.
I also like the ZSH shell, because is much more customizable than BASH. It has the Oh-My-Zsh framework, powerful context based tab completion, pattern matching/globbing on steroids, loadable modules and more.