If you're looking at flash memory-based players, you've already resigned yourself to a limited amount of storage. Still, the more, the better, right? Adamond's ZK1 player has 2GB of memory—the most in any shipping flash player, they claim (although players that take swappable memory cards would certainly challenge that, in their way). The Register finds it quite capable, in a not-quite-glowing review that scores it at 75%, but implies no great shortcomings overall. You pay for the capacity—more than a 4GB iPod mini—but it's smaller, plays OGG, and has an FM radio and recording features, to boot.
Adamond ZK1 2GB Flash MP3 player [TheRegister]