Here's my idea for a really cool festive 3D printed Jack O' Lantern with an LED light source that can be plugged into any USB and, can be made at home, with any suitable USB and bulb. I used Solidworks 2012 for this project.

Step 1: Starting

You start off by making an egg shaped sphere. Give it a colour that will resemble a pumpkin's, or any other colour that you want.

Step 2: Shaping the Pumpkin

Next, use 'circular pattern' to multiply the egg 9 times. Use different degrees of repetition for different pumpkin sizes and shapes.

Step 3: Making the Stem

Use the 'swept' feature to make the stem, and again colour it in any colour you want.

Step 4: Hollowing the Pumpkin

Use the 'shell' feature to hollow out the pumpkin- just like in the real life, but no mess...

Step 5: Carving the Face

Well, this is the fun part where you need to use your creative mind.
First you need to set a new plane outside the pumpkin. After that, use 'extrude cut' on that plane and shape the face in sketch mode.
cut it out. You can make any face you want- happy, sad, angry and such. Be creative about it.

Step 6: Making the Base

Use 'Extrude' at the bottom of the pumpkin we created an make a hollow cylinder. Color it in any color you want.

Step 7: Making the USB Connection Part

Now we'll make the USB connector part. Use the 'Extrude Boss' feature to create a rectangle, and hollow it out, at the beginning in the width of the USB cable that you will use, and later on make it narrower, so the cable itself will be able to pass through but the USB itself not. Use 'Extrude" again to make a cylinder the width of the outer circumference of the base we made. On it, use 'Extrude' again to make a hollow cylinder, so that the cables will also be able to pass through there. (in the photo it isn't hollowed out, but it should be). Make the circumference of the cylinder just slightly less than the inner circumference of the cylinder on the pumpkin, so it'll fit when we're all done. Color it.

Step 8: Attaching the LED Light

After you've finished creating your pumpkin, place an LED light inside (you can use hot glue to glue it onto the top of the base), and attach the plus and minus of the USB cable to it. Once you've finished, you can also glue the USB holder and the base, and also the USB to its place. you can now attach this to anything you want, and voilà-You have a USB LED Jack O' Lantern!