Ive made an ant with a harddisk motor once:
http://www.bugs.nl/images/Harddrive1.JPGhttp://www.bugs.nl/images/Harddrive1.JPG
http://www.bugs.nl/images/Harddrive2.JPGhttp://www.bugs.nl/images/Harddrive2.JPG
It was withing the weight limit, but no armour or anything. I have to update the micro because I speedhacked the servos and now its uncontrolable.