Various Impulse Buys For Games
Almost this, although I never regret it instantly.
Instant regret is what I get when I buy yet another mouse I don't need, although that's not so much regret as it is common sense yelling "you have enough already, you don't need more, certainly not at that price!"
There are few mice I still regret buying though.
And my new calculator, it was the most expensive one in the store and I will probably never utilise the features that I paid extra for, but it was the only model number I recognised from the list of recommended calculators and I was already familiar with it as I used to have one a few years ago that I since gave to my sister.(I didn't buy the same calculator twice, the first one I got as a gift and had no idea it was that expensive)
Edit:
Various Impulse Buys For Games
AH yes happens to me too, and I buy my games on steam so not like you can even return it
I believe this was taken to court in Germany not long ago and it was decided that according to EU laws all digital games(and probably digital goods in general) should be able to be sold on, although so far Steam hasn't done much about it, but that might be their plan for the new Steam marketplace. I sure hope so, because that means I can hopefully get something out of the games I bought but will never play.