Originally designed as a means for pilots to keep track of the clock in dual timezones, the GMT watch is an excellent tool for frequent travelers and international businessmen alike. But you'll be hard-pressed to find one beefier than Lum-Tec's Combat B38 GMT. This impressive timepiece is equipped with a Swiss Ronda 515.24 movement housed inside a 43 mm 316L surgical stainless steel case equipped with an MDV luminous-coated dial and hands, as well as a military-grade anti-reflective coated sapphire crystal. And its solid construction gives it an impressive water-resistance of up to 200 meters in depth. Add to it the fact that it comes with a lifetime of free battery changes, seal cleaning, and pressure testing and this might be the toughest GMT watch ever made.