What items have you bought at full-price and why?
I've purchased my A.P.C. Half Moon bag at full-price because after watching it for two years I found the damn thing will never go on sale. Now I can move on with my life because it's my HG purse that checked off a lot of requirements (minimal hardware, no logos, looks small but still holds a bunch of my crap, etc.)

Do you ask yourself questions before buying something at full-price to justify the cost? (i.e. Does this go with at least 5 other things in my wardrobe? Will this fill a wardrobe gap? Is this item more than my rent?)
The bit about it being more than my rent sounds a little crazy, I know. But I usually compare bigger-ticket items (leather jackets, boots) against the cost of my rent and it keeps me in check. Otherwise, I make sure I can wear it with 90% of what's in my closet, no questions asked (you can probably guess I only wear neutrals).

Does having a gift card influence your decision (i.e. "I'd never spend $70 on this t-shirt but I have a $100 gift card, so why not splurge?")
I'm kind of struggling with this right now. I have a $50 giftcard to a $$$$$ boutique I will probably never buy anything at, so I'm debating buying a $85 t-shirt that has the perfect amount of drape, but I still feel like I should wait for a sale. If I drop my Chipotle burrito on the shirt (which I do), how crushed would I feel? Should I use that $50 towards something more substantial?