Generic medicines

New cars. After a car has been owned by one owner, for however short a period of time, it dramatically reduces its price. At least in the UK.

Water

Reading glasses.

Air filters. For car, HVAC, etc. Branded or OEM stuff is usually overpriced.

Dishwasher rinse aid.

Hot dog buns. In my opinion, the generic, white, store brand buns make the best hot dogs.

Things like gift bags, disposible table cloths, tableware.... Get all that at the dollar store.

I don't cheap out on things. Rather, when I'm shopping I'm already looking for something that fills the need and is inexpensive. That's the goal. The default stance is to spend as little money as reasonable.

Liquor in general. Don't buy the cheapest shit on the shelf, go for the 25-50 range and you'll be set. Unless it's something you're passionate about and enjoy exploring there's no need to spring for the expensive booze. Liqueres and assorted (non liquor) cocktail ingredients on the otherhand... go for the genuine article. 99% of the time you'll still be in that 25-50 range so I hardly see a point in being cheap with them

People are gonna pillory me for this, but flashlights.

First off, you want something that runs off two AAAs, regardless of price. If you can't walk into any gas station, or any grocery store, or what have you, and buy batteries for your flashlight when it dies, it's not gonna matter how bright it was before it died. You also don't want anything brighter than ~200 lumens at the very most, unless you actually need one brighter, for some reason; they drain batteries way faster. You want something thin enough that you're able to clip it inside your pocket and forget it's there. You also want one that has an end switch that toggles between two modes: "full power" and "turned off." If you have one that toggles between low and high settings, you will only use the high setting. If you have one that toggles between low and high settings, and strobe and SoS, you will only use the high setting. Every additional step in between "all the way off" and "all the way on" is just friction you don't need, that will do nothing but piss you off every time you use the damned thing.

The features that make big, fancy flashlights expensive, are anti-features.

T-shirts. Get a 5 pack each of white, black, and another color you like. There, you're set for like a year for $30.

Headphones. Once you get to the $300 range, the more expensive ones sound different, not necessarily better. I have some electrostatics that have great extension, but the “real” sound is so harsh after a few hours.

For most people, tools. Most tools will be able to complete the essential tasks. Most people will get by with cheap or used tools.

I have a motto "cheap gets the job done, expensive does it faster". If you are a hobbyist working on your own time there, feel no pressure to get a "real" tool. Additionally if you are a hobbyist short on personal time, you might want something better.