I love my 24mm f/2.8 AI on my F3 it's been a wonderful lens to shoot with. I also really like the 50mm f/2 I have the non-AI H version but I just ordered an AI version for a comparison. Something tells me I'm not going to find a world of difference. This lens is seriously impressive.
I also recently got the 105mm and its every bit as good as people say. I have the older Sonnar type and it is quite nice.