This one uses a vibrating motor from an old cell phone, a 3V watch battery, and a paper clip. A little soldering, some hot glue, and you've got a vibrobot!
Step 1: Gather Materials
1. A watch battery (I used a 3V, but you can probably use whatever you find)
2. A motor from an old cell phone
3. A big paper clip
4. Soldering iron, solder, flux (optional)
5. Hot glue gun
6. Electrical tape
7. Sharpie or other dark marker
Optional but helpful:
8. Metal file
9. Rubbing alcohol
10. Needlenose pliers for the bending
Step 2: Make the Legs - Part 1
First, straighten out the clip, then mark out six equal parts. On mine, marking every 1 1/16" worked out fine.
An important note about bending the paper clip -- go slowly! Take a few seconds to make each bend, or it could snap. Also, for the angles that are greater than 90, make them rounded, so there's not so much stress at one point. It took me three tries to finish the legs. (See the last photo.)
Now, bend a 90 degree angle at the first mark.
At the second mark, bend it back completely.
Step 3: Make the Legs - Part 2
Step 4: Make the Legs - Part 3
At the fifth mark, make a 90, angling it away from the other two adjacent legs. After this step, you should be able to set the legs down, and have four points of contact. If not all four points touch, gently bend them until they do.
Step 5: Attach the Motor to the Battery
Scuff up the bottom of the battery a little, I think it should help the solder and hot glue adhere. I used a file to mar the surface. Make sure you clean it afterwards with a little alcohol. I believe acetone will work better than rubbing alcohol, but use whatever you have around.
Your motor should have two wires coming out of it. Solder one wire to the bottom of the battery. I had trouble getting the solder to stick, so I reinforced it with a little electrical tape (which you can't see in the pictures).
Step 6: Attach the Legs to the Body
First put a fairly thin layer of glue over the entire bottom surface of the battery.
Now stick the legs on, keeping the three points of contact away from the soldered wire. Once you're happy with the placement of the legs, put a generous amount of glue over the points of contact. Don't be stingy!
I used a small piece of aluminum and line level to keep the plane of the feet parallel to the plane of the body. This is completely unnecessary -- you can just stick the legs on and they will be fine.
Wait for it to cool -- I stuck mine in the freezer for a couple of minutes to hurry the process along.