I did a good number on my truck last weekend! Battery died up in the mtns up a jeep trail and had my roomie bring his car as close as he could and i hiked his battery up and was putting it in my truck to start it and get it down the trail to a main road....put the battery in and was putting on terminals and his posts were smaller than my terminals so it sparked quite a few times while i was wedging a nail in between....windsheild wipers started going on their own and the truck would just turn over and not fire.
I got a new battery the next day and went up and swapped it out and it started right up. Then I found out what all I messed up!
-Blew HID Ballast boxes
-Blew 120amp ALT fuse
-Blew fuse on the back of my head unit
-Phone Car charger doesn't work anymore
-Cigarette lighter doesn't work
I'm not as worried about the last 2 as long as it runs and i got tunes but I've never heard of so much going wrong just from sparking a few times while putting NEG terminal on!

 

well now you have,and we will all make sure never to do that!

 

holy crap

 

Jeez