Apple.
garage sales
Small stores. They’re not overwhelming and so you don’t really feel like it’s too much to go browsing up and down a dozen or so aisles. My pharmacy is this - bastards. And they must know this since they have at least 2 aisles of nothing but tchochkes. But it’s the 2 stationery aisles where I really get my kink on.
However dollar stores are the pure distilled essence of evil. They don’t have actual “departments” really so you can’t plot out an itinerary like you would at say Target and even if you could, you wouldn’t since that’s not usually the point of going to one.
You’re almost obliged to go down every aisle and for a buck, who can’t use yet another caliper or adjustable wrench - even if it is a piece of shit.
IKEA was what popped into my head when I read the first sentence of the OP. Must resist colourful kitchen thingamabobs.
Costco is bad too, I can go in for one thing and spend $300.
Here’s an odd one: Wineries. They suck you in with free tastings and you end up with a case of wine, an $80 wine opener you’ll lose in a week, plus a cheese knife you will never use.
Grocery store. Because by far most of my shopping is at either the commissary or the local supermarket.
REI
Spencers, Hot Topic, Tiger Direct.
I always go in those looking for one specific item, and leave with more.
Academy/Cabellas - always some cool camping gear I didn’t know I needed until I see it.
iTunes - lots of impulse purchases here. Listening to random samples is dangerous.
Bookstores. And supermarkets if I find any great looking curries or something.
My big obstacle though is if I visit our local antique store. It also sells a lot of stuff which would probably qualify more as junk- but how could I resist that 1904 Ansonia Clock? Or the 1915 White treadle sewing machine?
Grocery Stores
WalMart
Target
Pretty evenly between the three.
Any store that sells hats. If they fit, look good, and are under $20, I can’t resist.
Bookstores and grocery stores, of course.
Definitel thrift stores. I go to the local ones so much that they know me and give me additional discounts.
I have a butcher shop near my workplace. They’ll sell me a thick sandwich, chips and bottled soda for five bucks. But I never leave there with less than $25 worth of food because I always see something that I just need to buy for dinner plus some sausages or hot dogs for the fridge plus the horseradish sauce they sell, etc.
Dollar stores. Thrift stores. Anything I can justify to myself by thinking what a great deal I’m getting.
And purses - one of my only “typically girly” passions: the pursuit of the perfect bag.
Lee Valley is one of those stores that always throws in* an item or two more than I had on my list. It’s a long standing joke at home already 
*Generally for the cost of the “thrown in” items
The grocery store. It is a very, very rare day that I walk in with a list and walk out with only the items on the list. It’s the biggest money-trap of my budget.
Von’s. Not the well-known grocery store chain, but a local hipster store in my old college town. They had beads and books and all this weird handmade paper. Paper with flowers embedded in it, parchment paper, artfully pre-wrinkled paper in tons of colors. It was always a fun place to browse. I’d go in with $10 in my pocket and come out with some seriously cool, unnecessary shit.
Sams Club. They always have some cool something, whether small or large.
Sadly, auto dealers for me.
My 4 vehicles prior to my current one were all impulse buys with no previous research. Basically, just me deciding to see cars, liking one at the first dealer I step into, and then signing away for the purchase/trade.
Because of this, I try to avoid the sales floor when getting services done.
I was thinking more “Orange f—ing towel”, but whatever 
Old Time Pottery, for me. I almost always walk out with something. Cheap kitchen gadget, new dishtowel, throw pillow. I’m still not sure how I ended up not taking home the pig salt-and-pepper shakers I saw last time.