Hey,
Obviously people aren't too quick to divulge their #1 selling products lol.
I would recommend starting with something like iPod accessories. I am in the accessories game, and I am making between 300-400% mark up. Everyone seems to want these things, plus they are cheap to buy, and the potential loss is reasonably small.
Whilst the profit margins aren't huge, over time, it does accumulate.
Cheers,
Tom