Here's our table: On a natural 1, you roll on this table.

Fumble Table
1: Damage self for 1-8 hp
2: Damage self for 1-4 hp
3: Hit nearest ally for regular damage
4-6: Break weapon; magic weapons get save
7-15: Drop weapon; lose next round's action
16-20: No fumble; weapon slips but grip is regained

For spell failure, we've cribbed from DCC as follows:

¬   Always check for spell resistance/misfire with d20 roll or more if multiple actions in play
¬   If a spell fails due to the caster rolling a 1 or due to a creature's spell resistance, there are potential repercussions
¬   Divine casters must make a Charisma check or incur deity disfavor as per DCC
¬   For arcane casters, they must roll on DCC spell misfire table & they must make Charisma check with DC at spell level and if 
        that fails they incur corruption as per DCC
¬   Spell levels 1-3: Minor Corruption; 4-6: Major Corruption; 7-9: Greater Corruption