Fish shell
Pretty flashy :-) I like how it told me to use () when I tried typing $(), and the autocompletion is quite impressive.However, how do you work around the lack of ()? E.g. if I want to do the equivalent of    $ diff <(xzcat foo.xz) <(xzcat bar.xz)

?EDIT: nevermind, I see the fish version is    $ diff (xzcat foo.xz|psub) (xzcat bar.xz|psub)

which actually does the mkfifo dance for you :-)