My TV.
Either that or the PS2. Specifically, Slim edition. Gaming-wise, it was definitely their biggest achievement on their own. PS1 doesn't count because they had a TON of help from Nintendo in creating it, PS2 Phat is out because it's ugly and huge, and PS3 doesn't count because it's too niche (PS2 in general wasn't considered a "gamer's console". I know very, very few casuals who own a PS3, though).
Or maybe Walkman. Thanks to the Walkman, portable music players became commonplace. If it weren't for the Walkman, portable CD players (like Discman, etc) would have never come to be. If portable CD players never existed, we wouldn't have portable MP3 players (iPod, Zune, Zen Vision, Walkman MP3, etc). If not for portable MP3 players, modern smartphones (iPhone, Droids, Samsung Galaxy, etc) likely wouldn't exist. And, of course, if not for modern smartphones, modern tablets (iPad, Kindle Fire, Samsung Galaxy Tab, etc) wouldn't exist.
The Walkman brand may be tremendously obsolete nowadays, even if it's still around, but the modern infatuation with smartphones and tablets was only able to come to fruition thanks to a snowball effect started in 1978 by Sony. It has most certainly solidified its place as a worldwide lasting game-changer; something few devices can ever claim.
SW-5120-1900-6153
