Not a Proud Moment: 
While tightening the battery termianl on a lawn
tractor battery, i shorted across the terminals with my wrench just
like any ol' Bubba could.  The explosion happened so quick i didn't
know what blew up, i stood there in an auditory shock wave (complete
silence) with my jaw dropped to the floor looking around to see who'd
just shot a high-powered rifle off point-blank.  THEN i noticed my
hand was bleeding and i had acid all over me; the case on the battery
lay in shatters.  I ran into the house and jumped in the shower...
no real damage except to my clothes.  Very lucky.

the old rule of remove the negative cable first, put on last is a 
good one but wouldn't have helped in this case 'cause i had laid my 
wrench across the terminals.  Needed to get back to a more basic 
rule...  Don't work while your head is up your ass.
-dan