A cow and a tractor
The farmer goes to town one day and happens to run into his old pal the tractor salesman. "How's business?" asks the farmer.
"Not very good, I haven't sold a tractor in months, How are things on the farm?" asked the salesman.
"Well-- The other day I went out to the barn to milk that old cow I have. I started milking and she swatted me with her tail, so I tied her tail to the ceiling.
I started milking again and she kicked me with her left leg so I tied that to the left side of the stall. I started milking again and she kicked me with her right leg so I tied that one to the right side of the stall.
About that time my wife walked in the barn, and if you can convince her that I was just trying to milk that damn cow, I'll buy a tractor from you!!"