I should say beforehand that I am probably missing some things. Also, I am a terrible over packer. I over pack, always. I also spill on myself a lot, hence extra clothes, so do what's right for you.
Clothes:
-1 pair of pants (red ones maybe also pink ones)
-1 pair of shorts
-4 shirts (1 nicer one, 3 fandom ones--blue&white stripes/tan&white, b@man, last year leaky, etc.)
-6 pairs of underwear
-4 pairs of socks (Hogwarts+TSK)
-A GOOD PAIR OF WALKING SHOES. (my star converse)
-a pair of flip flops because pool (me: TSK ones)
-swimsuit and towel (even if you don't think you'll swim, bring a suit because you never know!)
-sunglasses! (thanks, judyandthecat!)
-yoga clothes (yoga pants, tighter t-shirt, yoga mat/towel)--if you plan to go to yoga
-a casual dress (in my case--the purple one)
-if you want to wear concert outfits, bring those. (red skirt&white tank top, grey tank&another skirt?)
-dress for the ball (blue one)--people wear all sorts of things, so you don't have to have a dress or nice clothes. just wear whatever! (also bronze heels though i'll take them off)
-FOOTIE PAJAMAS (kelsey what are the size on the ones you have?)
-pj pants&shirts (1 pair of pants/shorts, 2 t-shirts)
-jewelry (pig&duck earrings&hallows necklace)
-Costumes (for anyone who has them):
-----Robe, sweater, white undershirt, white shirt (button up; 2, one short sleeve one long), skirt (2, short&long), tie, socks, shoes
Toiletries:
-shampoo and conditioner (note: if you are flying, REMEMBER THE SIZE limits. also if you don't have a lot of room in your bag, talk to your roomies--maybe you guys can all share.)
-razor/etc.
-toothbrush&toothpaste&floss
-deodorant (and maybe baby powder because chaffing)
-tampons/pads/liners/cups/etc. if you need them/are cautious
-any hair things (brush, hair ties, bobby pins)
-make up (concealer, powder&brush, probably will paint my nails blue&bronze pre-con but I have ALL the houses so is anyone interested?)
-anything else you use on a daily basis (lotion/q-tips/etc.)
-if you plan to hang out in Chicago before/after the con on the beaches/at millennium/etc., sunscreen.
Food:
-box of crackers (Wheat Thins fix perfectly into my bag last year)
-some granola bars
-a reusable water bottle (seriOUSLY)
-tea bags/etc. if you're a tea/instant coffee/flavored water person
-possible: small sodas (if you really want)
-possible: instant macaroni/etc.
-possible: a jar of peanut butter and a loaf of bread.
Last year a kid had a bag of Tostitos so.
NB: have food money set aside!
[And hey, my room, since I'm so close I think I may bring bagels, bread, and peanut butter. also maybe juice boxes.]
Electronics:
-phone&charger
-iPod&charger (optional: speakers)
-optional: laptop (I think wifi is $8 in the rooms idk if they have complimentary anywhere and I may not bring mine this year we'll see)
-some people bring their Kindle so that and a charger
-camera and charger! (thanks, judyandthecat!)
-if you're not from the US, adapters. (thanks, judyandthecat)
Other:
-any medications you need (me: Zoloft)
-a small ziplock with ibuprofen/advil, bandaids, and anything else you may really need (emergency medical info is good to have)
-IDENTIFICATION granted if you're traveling you'll probably remember this but still
-YOUR WAND, WIZARDS. BRING YOUR WAND. (and put a piece of masking tape on it with your contact information BECAUSE PEOPLE LOSE THEM ALL OF THE TIME)
-anything you want signed. (me: Looking for Alaska, Anna&TFK, TNOTS, picture of Oscar, HP7, possibly H:AH, Warblers CD)
-gifts/letters/etc. (I need to write my TSK/nick/denise letter)
-they will give you a bag at Leaky to carry your stuff in but if you want to be careful bring one anyway
-money/cards/etc. (if you have subway/etc. giftcards it is not difficult to find food in Chicago so these are USEFUL)
-notebook to write in/for your friends to write in/etc. (thanks judyandthecat)
-printed leaky registration and printed schedule if you organized yours (if you didn't, you'll get a copy of the schedule there, it's just if you color coded/etc. beforehand) (thanks judyandthecat)
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If there's anything you think I've forgotten, let me know and I'll add it! Hope this helps people who are overwhelmed/lost with where to start. :)