I like the LaCie "Rugged" series with Thunderbolt and USB 3.0 interface. I usually get them as a "refurbished" unit from MacMall and either use them as is, or swap out the hard disk drive for a SSD. Currently they are $80. If you don't like the orange shock bumper, it is easily slipped off.
http://www.macmall.com/p/LaCie-External-Hard-Drives/product~dpno~9597442~pdp.icbeahb
Judging from the number of posts on Apple's discussion fora about USB drives unmounting randomly, I would still (and actually do in my usage) prefer Thunderbolt drives to USB3 ones. Apple still has issues with USB3 drives randomly ejecting.