I don't think this happens much anymore because information is easily available but what are some purchases you've made where you had no clue about the game but it looked cool?
Two really good ones come to mind for me:
Mario Kart - this was more of a gift and I had never heard of the game (living in Italy at the time probably didn't help the fact) but after playing it for a few minutes I knew I would play it for a long time.
Suikoden - It was my birthday and my parents took me to CompUSA and told me we weren't leaving until I picked out a game. I saw the box art for Suikoden, looked more interesting then Beyond the Beyond and bought it (along with a copy of EGM2 that had a guide by coincidence). Now it is in my top 5 games I've ever played.

