If you want something that will resist shocks and without cable clutter, I would consider a low-performance 2.5" SSD (high performance would be wasted in an enclosure so you save money) in a USB 3.0 enclosure that has the USB cable built into it. I wouldn't buy a USB 2.0 device anymore if you have a 3.0 capable computer.
Something like this is pretty convenient to have no stupid cables.
It all really depends on your budget. An expensive rugged case has to prevent shocks and vibrations from damaging a mechanical drive and will be big and heavy but an SSD doesn't need that as it has no mechanical parts. An el-cheapo metal case for $15 is perfectly fine. Furthermore, the chips of an SSD are already inside a casing as well.