The torpedo-shape Zojirushi is airtight when the cap is battened down and the safety lock is fastened – you can chuck it into a backpack or briefcase with no fear of leakage. Sure, taking a sip involves popping open the Pez-dispenser-style lid, but that's a small price to pay for a mug that kept our coffee piping hot for seven full hours. [$42; zojirushi.com]