I was just thinking, can I honestly think of a perfect anime? But yes, Steins;Gate, without a doubt. It is so perfect that the second season, which is an almost-perfect anime and fits neatly in the events of the first, can only bring it down in perfection.

I recently rewatched it and there's a lot of foreshadowing and plot points that hit harder when you see them coming.

I love Stein's; Gate but those first few episodes pacing keeps it a step from absolute perfection.