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If it's about discounts, sure. If not, not so much, but e.g. some fast food ads you see outside can have stuff you might want to try. Beyond that, I don't remember buying much stuff because of ads, but it probably does happen every now and then. Of course I see a fairly limited amount of ads since I don't watch TV and I use adblock on the internet.

Mostly I think ads, are wasted on me.... not saying Im immune or something, but I rarely think they actually make a differnce.

What works?
Product reviews... if you want to buy something, today its easy to go read a review (or watch) of X product.
Sometimes if the product review is very postive, and you really do wanna go get X product.... it ll be the last little thing that throws you over the top, and go you buy it. Esp if its a thing on sale too, its like nows a good time to buy it, and this review was very positive... done.

With video games, I think gameplay videos is a much better "sale" effect than just a poster or such.
As others said, a ad is more like a "reminder" that something is soon out.

I dont buy something before I see actual gameplay these days though.
Have to watch it, and think, this looks well done, or could be fun.

McD does this alot... and it works (atleast on me and my family, from personal experiance). 
They often change up the formula, or now with a new x,y,z... and it does get you to go try it out.

Only when it reminds me that i need it

Its hot.... your thirsty,.... and suddenly you remember...

(in the old days)
The bottle opener clinking against the glass bottle, the bottle opening, the cap falling and landing and rattleing abit before settleing.
You hear a glass placed before you, and the ice cubes pored in.... and the fizz and crackleing from the ice, as the coke hits it.
You hear the ice cubes running around the glass,...

Then theres that "aaaaahhh" as the guy takes a drink.

Visually theres those sweat pearls along the glass, and it just looks like a million bucks (on a hot summers day atleast), that glass of coke.

Its like one of those AMSR videos or something.
Cola was ahead of the times man.... you watch one of those days 2-3 times a day all year long.... come summer and your thirsty... your thinking
"I could drink one of those cold glasses of cola, right about now"

Hell Santa used to be blue..... but Coke's logo was red, so they changed his outfit to match the logo's colours.
Cola used to be more expensive (compaired to today), so it was something more often used to celebrate with... Cola wanted in on the christmas market. They ran ads, every holiday with Santa in red.

Today everyone "knows" santa wears red.

I'm fairly sure they're very effective in making people buy certain things, I mean if you have them you need to get treatment for basic illness's or you will die as you don't have your immune system.

I don't think so.
Sure when I was a kid I certainly asked a lot of stuff because of ads, and as adult some ads have showed interesting stuff that I researched and bought after. But buying because of the ad I don't remember doing. I'm to controled on this.

Sometimes when it was new ad and a new product, just to test it. Most of the time, it stayed at that one test, because it couldn't beat the product I was using until then. But sometimes, it did, and then of course I bought the new one instead of the old one. However, I don't think that this happened more than 6-7 times in almost 20 years now.

Just to remind marketing is more than ads. And winning mindshare and translating that to more sales is the objective. Impulsive buy is a more rare occurance.