I've had a few higher end models( IPOD, Creative Labs), but I have to say the most bullet proof one I've had yet is the RCA Lyra I got for free through a promo deal. It's about $40 at walmart now. I'm an avid long-distance motorcyclist(approx. 50k miles/year, and on a sport bike, so high speeds). I ride in all kinds of weather, and usually very aggressively. This thing went through 2 full seasons anf part of another, and has never let me down.
The one I have is an older model, and has an SD card slot, which is VERY nice. I have bunch of SD cards laying around, so I can load all sorts of different music and have miles and days of fun..
However, it is VERY simple, and the one thing I will give the IPOD(which broke in 3 weeks, and that was just from vibration), it did sound better on my Etmyotic ER6i headphones.