Casio M5610U with a metal mod I picked up for $99 and I love it! Pick up and go with never a care for durability or accuracy. World time across 5 presets, that you can swap back and forth with your home time at a press of buttons, solar powered, and radio receiving for auto updating of time and date.
What's your cheapest watch in your collection?
It's a multi-way tie given that I have a few colors, but a Casio F108. They're like $18 dollars at WalMart last I bought one.
The battery life is crazy too. The one I've had the longest has to be reaching the 10 year mark and it's still on the original battery.