here's a ton things to do with sharpies! I'll try to add more! Comment your ideas!
01- Decorate your canvas shoes- Converse, Vans, Keds, whatever. Be careful doing this as you can't get them off. You can do whatever you want- draw words, doodle, or even do Missoni zig zags (see @polyvoretipgirls 's great tip: http://www.polyvore.com/zigzag_sneakers/set?id=37910758&lid=1235903 )
02- Use them to do tie dye! It looks really cool and it's easy! (credit to http://www.designmom.com/2011/12/diy-sharpie-dyed-underwear/# ) you need cotton whatever (tote bags, shirts, shorts, headbands, whatever) and cover surface with a dark towel. Color whatever design you want in sharpies. Carefully drip rubbing alcohol onto the colored area. Let it dry completely before flinging it into the clothes dryer to set the dye.
03- Quote book cover! See above photo. Just use a composition book and doodle on it!
04- DRAW! No brainer, girls!
05- doodle on a light switch cover
06- Design your shirts. Put a piece of cardboard inside your shirt and go crazy (or not). Ideas? The Chanel logo, doodles, words, triangles, etc.
07- Personalize your white cut off shorts. Just doodle. This looks so cool.
08- Shrinky Dinks! Oh my gosh, I LOVE these. You can get plain shrinky dink paper (get the type with 'frost' on one side, and shiny clear on the other.). These are really easy and fun- just draw whatever on the paper, cut out, punch a whole, and shrink (it will shrink to 1/3 of the original size.). It will also thicken. I've made many very cool earrings and necklaces and bracelets doing this.
09- Decorate leather bracelets. Buy widish plain leather band with a snap and start drawing. I did this and it turned out soo cool.
10- You can use these as temporary tattoos on your body. Just draw and they'll disappear after a while.
11- You can decorate cups... a lot of people do this and take photos. They look really cool and you can just use them as pencil holders or whatever you want to.
12- Use them as nail polish. Paint your nails with 1-3 coats of neutral nail polish (for protection), clear, or nude. Add a layer of sharpie. Do not add a layer of nail polish. Credit to @the-amazing-tip-chickas
13- When Easter rolls around, decorate them with sharpies!
14- go mustache bombing- draw one on anything and everything.
15- design TOMS.
16- Make posters
17- decorate a pumpkin at Halloween
18- decorate dominos
19- draw on t shirts
20- cover a couch.
21- add things to photos (especially black and white)
22- write all over your old yearbooks
23- Buy an old book and draw in it, over the words.
24- draw on cups or flower pots.