Mostly gaming/gamedev/dev related subreddits. Best source of getting fresh links/info imho, fast and clean. As for "opinionated" subreddits where people "discuss" things and share their "views" and "opinions" about "stuff", have enough of that in here. Tried to use it for porn but that doesn't work very well so far because I mainly use it for getting links to serious stuff and honestly, can't mix those two.
Wish twitter was organized in similar manner, don't like their concept at all. But twitter, combined with g+ is by far the best way of getting stuff I need for my line of work. Reddit has way too many fake experts, sprouting bullshit "facts".