+1 on Scepter gas cans. I have several and have been using them for 4-5 years, winter and summer. They are quite tough, and they seal very well. If I'm careful while filling, I don't get that gas smell in my trunk. Hint: leave room for expansion to avoid gas-stink; only fill 3/4 full and squeeze the sides in with your legs before you tighten the cap.

That said, I only transport gas from A to B. I would echo the concerns expressed here about having a can of gas in the trunk at all times.