Kimi no Todoke. This series had an ending that seems like an anime ending tacked onto an ongoing manga. They could have left off ep. 12 and left themselves more room for a continuation, but what the hey. It was getting kind of repetitive anyway. The last episode was not very strong.

Hourou Musuko. I think ep. 11 was the last episode. At any rate there were no previews and they omitted both opening and (usual) closing credits, which is normally the sign of a final episode. T Man wanted to know how it ended: