My name suggestions would have to be Death Note, Clannad & Fate Zero.
Log Horizon, Madoka Magica and Code Geass are also good choices though.

[quote=Rare]I think you should watch Boku No Pico[/quote]

[youtube]4F4qzPbcFiA[/youtube]

[quote=Vortex]I've seen the movie... Does that count?[/quote]

Not as an anime.
And it also barely does the show or manga any justice.
Do yourself a big favor and go watch the anime or read the Magma.
It does the series far better justice, partly because it gives it more time to flesh people out, explain the plot and explain the complicated plans at work.