I foound 2 chemicals that do work to remove marks and burnt in fingerprints and such rather well from the rubber part.

1. Ecosense Tub & Tile
2. Concentrated Goo Gone (which by the way is certified by and used by Apple when re-manufacturing/refurbishing and in apple certified repair shops). As for the little ding i would have to say lightly use a black silicone sealant
Mobile-2.2Ghtz Core 2 Macbook, 4GB ram, 160GB HDD
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PC-C2D 2.4Ghtz, Asus Commando, 2Gb ram, 3 hdd's in raid 5, 8800GTS.