The last goal by Vanpersie. The one ruled offside. From the replays I saw, I thought it was fairly close, and if indeed the benefit of the doubt should be given to the attacker, it was a valid goal.
Not going to moan about refereeing standards, as they have always been relatively poor in the premier league. Don't think there's much to the bribery or corruption claims either, but there is definitely a clear bias against Arsenal most of the time, and for me, it's all down to xenophobia and dare I say a bit of racism.
The media also doesn't help matters much.