Behold what may perhaps be the most famous Warhammer 40k conversion ever. The Hover (Deodorant) Tank!
Rick Priestly wrote perhaps the first full conversion article for 40k featuring the Hover Tank in White Dwarf 95 many, many, years ago. He built it off a deodorant bottle, and various bits.
Behold the splendor of the Hover Tank, kids don’t try this at home! -MBG