Cool Glasses - As someone on the spectrum who is below-average in terms of physical attractiveness, the one thing I sorely lack is rizz. The ability to put on a pair of glasses and be able to automatically pass any job interview, make any new friends, sell any product, chat up any woman, etc would be massive. Also, no cooldown.
Fatigue Masking Mask - Gaining an extra 7 waking hours of time in a day is massive. If you're productive this is the artifact to go for.
? Tier:
Caffeinated Shoes - This item is either moderately (C) to insanely (A) useful depending on its limitations. If you can skim across entire oceans at superhuman speed then that's massive. If you lack superhuman reflexes and will get splattered into a fine bloody mist from colliding with anything then it becomes a lot less useful.
B Tier:
Frying Pan of Flavor Town - Unless it's a massive cast iron pan, don't expect to be opening up restaurants with it. It's best reserved for your own nutrition and impressing guests with your cooking.
C Tier:
Lucky Penny - A 50% chance of having incredible luck for twelve hours once every fortnight seems great, but the cooldown is prohibitive. Also, unless RNGesus has bad luck protection, there is an incredibly slim chance that none of the 2000 or so times you get to use this item will yield any changes. Also, good luck can still wear off after those twelve hours.
D Tier:
Underwear of Fe'Breeze - Personal hygiene doesn't take up much time, and with the right environment and lifestyle you can easily build up a habit. This one is just the least useful.
I agree with all of this except for the penny. If it makes everything you try go right for 12 hours, you could do some pretty awesome and life-changing stuff, even if it has a long cool down! It could be A or S tier depending on how you use it
The shoes are really a wild card on the list since they are percentage based. On Usain Bolt they might as well be the Winged Sandals of Mercury, but on my flabby ass they'd just make me a fairly competent runner.