I hope you find these useful. Both scripts can be used as a one-click-install in the Roll20's script dropdown under the Character section. Critical - A quick method of determining the outcome of a critical hit. Fumbler - A quick (and often humorous) method to determine what happens to your players when they fumble. Also, the Markov script I created earlier last year is now available as a one-click-install.
I have been using a rollable table to generate Crits and fumbles, this is a nice change, thanks.
Thanks al e. I originally used rollable tables, but I found these awkward and tedious. I am currently working on letting users create fumbler handouts that have their own charts in JSON format. For example you can create a handout named fumbler-disaster with your chart in the Notes and use it in the chat as: !fumble disaster 92 92% Unaware idiot Hit friend, normal damage. See my fork of Roll20Scripts for my progress.