Which lens would be best for wedding photography?

I'm open to suggestions, but this is what i've narrowed it down to based on price range and preference:

Nikon 50mm f/1.8D AF
Tamron AF 70-300mm f/4.0-5.6

i'm aware that they are two completely different lenses, used for different purposes. But if you were going to be taking *unofficial* photos at a wedding and had to choose one or the other, which would you choose?

my cousin is getting married in a few months. She is not hiring me, photography is just a hobby of mine.
i'm also just in need of a new lens! I'm bored with what i have.

50 f/1.8 no questions asked. You have much more flexibility with light and dof and won't be so telephoto. The 70-300 just won't work for most shots because you don't want to be standing far away from everyone. Also be careful about the I'm bored I need a new lens thing. Thats a trap that a lot of beginners fall into. I did the same thing. I started out with a 75-300 and an 18-55 then it was a 70-200 f/2.8 then a 100 f/2.8 macro then a 24-70 f/2.8 then I needed the nifty fifty (50 1.8) then an 11-16 f/2.8. Nowadays? The 70-200 f/2.8 and a 35 f/1.4 and thats it. I keep the macro for a few select wedding shots, but everytime I go out its my zoom and my 35. Because I'm either closer enough to get real close or far enough that I need the 70-200. New lenses cure boredom for about a week if that. What you really need is to push your vision a little further. Keep shooting with the same lens till you start to see things differently.

I'd go for the 50mm f/1.8. Good lens, fast and sharp and will allow you to shoot in lower light. It is also a good portrait lens on a crop sensor. You can zoom with your feet.

The nikon's quite nice, the tamron is a budget tele, useless indoors. Both do not autofocus on anything lower than a d90.

For a wedding I'd treat myself and rent a 24-70 for the weekend