This Instructable is a part of the 3D Creation Systems Jack o' Lantern challenge. You can enter by posting your own design to the contest. It can follow these instructions or be made entirely differently in the CAD program of your choice. Just make something spooky!
OK, let's make a 3D jack o' lantern
Step 1: Make a Ball
There it is. A sphere!
Step 2: Squeeze It
Non-uniform scale of .8 in y axis
Step 3: Copy It
Make a copy of the ball and move it over
Step 4: Copy the Copies
Copy that pair and rotate the new pair 36 degrees
Step 5: Repeat!
Make 3 more pairs of copies and you'll have the body of the pumpkin
Step 6: Make a Curved Path
Draw a curved line
Step 7: Draw a Circle
Draw a circle at the endpoint of the path
Step 8: Extend the Circle
Rotate the circle to be perpendicular to the path and create the stem by following the path with the circle
Step 9: Insert Stem
Move the stem into place on the body of the pumpkin. You will likely need to change the scale of it
Step 10: Combine
Connect all of the shapes together
Step 11: Shell the Pumpkin
Hollow out the pumpkin with the shell tool
Step 12: Cut a Hole in the Bottom
Create a cylinder and subtract that from the main shape. You now have a hollow pumpkin with a space for a LED candle to be inserted.
Step 13: Cut a Face
Make your own face for the jack o' lantern by subtracting different shapes. When you're happy with the results you can export an STL and print it!