It all depends on personal preference. Some cases are thick like leather; others are hard plastic; and others are close-fitting plastic, similar to spandex. If you want something to protect it from harm, get a leather or hard plastic case; if you want to merely keep it clean, get a pliable case (in your choice of numerous colors or completely transparent) and make sure it has a screen cover.
I'm on my third iPod case. I used apple's case until the iPod slipped out of it. After that, I bought one of those skin tight leather cases.... That sucked because it was hard to get the ipod in and out of itand dirt seemed to collect there like crazy. I'm on my third case from Marware. Based on your requirements, I think that it fits your requirements...
The clip is very low profile and it stays in place without a belt (not something you can say about a lot of the clips out there). if you want to excersice with it, you can take the clip off and it has to belt loops that you can use with the enclosed neoprene armband so you can be absolutely certain that the ipod will not go anywhere no matter what!
The cover is removable and has a small pocket for the earbuds. when the earbuds are not there, the hard pocket is excellent protection for the front of the ipod. the case is also plastic reinforced on the back. the sizes and the bottom have thicker rubber which is good for getting a good grip and also good padding in case you drop the ipod.
you can also buy a neoprene belt if the arm band is not to your taste (it is not to my taste) and even cooler, you can buy a bike holder (which works with the optional swivel clip).
thanks javintosh... can i ask you one more question... how heavy is the marware case.. because i run with a small radio now which weighs nothing.. not that i cant adjust for the ipod and case.. believe me it will be worth the effort hehe.. just curious if its awkward.. by the looks of the pictures it looks good.. might pick me up one of them