Know any waste-of-money stuff?
Only using your razor blades for 3-5 shaves. As long as you clean and dry the blade, one insert is useful for literally hundreds of shaves. Also, shave in the shower (buy a shower mirror that suctions onto the wall for a fraction of the price of new blades). Dollar Shave Club? Hogwash. Try $0.33 shave club.
Bottled water is a waste if you have a Britta or in-fridge dispenser. My tap water has a very distinct chlorine smell to it.
Seltzer water. Soda Streams are under $70 (Less if you can find a deal on eBay) and they pay for themselves within 3 CO2 canisters. Clip Bed, Bath & Beyond coupons and recoup your cash even faster ($5 off coupons are better than the 20% off variety).
Pool algaecide. For the most part, if the water is otherwise properly chemicaled, PH balanced, and vacuumed, it's not worth it.
Selected name brand groceries such as beans, some cereals, condensed soups, frozen veggies, among other items.
Most insurances not covering the home, personal car (non rental), or wellbeing (i.e. health, life, LTD+D, etc.)