In discussing Magic Attacks vis-a-vis microlite20/74's "Magic Attack" mechanic, the subject of "natural 1s/20s" came up. If you are performing a Magic Attack (that subject itself has caused a bit of discussion when/how to use in the microlite forums), and the player rolls a natural 1/20, the GM might decide to invoke a houserule of fumble/critical hit.

This opens up a HUGE amount of possibility, especially depending on how the GM approaches the use of magic in his/her campaign. Is magic like 'technology' and more of a tool, rather than a force to be reckoned with? Is magic a wild and unnatural thing, and the possibility of a fumble could be an Ultimate Bad Thing and a critical hit an Ultimate Yesss-I-Feel-The-Power! moment?

I did a quick search on Google (fumble spell chart) and found this interesting set of weapon/magic fumble/critical charts (Microsoft Word Document) by David Nihsen. I've copied them locally, in case his server or this link ever dies, but in case I want to indulge the Great RNG in its Divine Randomness, these charts are very thought provoking! Not all of the mechanics are quickly translated to m20/74, but they give a lot of options towards your own fumble ideas.

91-98 Magic shoots out of caster’s nose like a sneeze. Caster loses nose. CHR is at 10%.

Bwah!