Here's a debate I did a long time ago at the University of California. The topic was "Who Was Muhammad? The Christian and Muslim Perspectives." If you'd like to have some fun while you're watching the debate, pull out a piece of paper and try writing down Ali's arguments for the Prophethood of Muhammad. You'll need about one line.
DAVID'S OPENING STATEMENT
ALI'S OPENING STATEMENT
CROSSFIRE & CONCLUSIONS
You can read some reviews of the debate here and here.