The mod souls in Bleach have a really bad rep and I can not really argue it. Kon, the original mod soul that we were introduced to was an actual part of the series, the rest were made from filler episodes.
There were four main mod souls being (image left to right) Kurōdo, Noba, Ririn and Kon.
Worst Mod Soul
The title for the worst would have to be Ririn, even though her abilities were decent. I found her to nothing more than a really irritating and a rather nagging character.
Best Mod Soul
For myself, the best mod soul was Noba, in both his ability and personality. He was quiet and shy he also cared about his fellow companions and he could teleport both himself and other people.
Which mod souls were the best and worst in your opinion?