One of the ads running in the Canadian market for Full Tilt Poker makes mention of the website's "realistic" poker sounds, such as the swishing sound of cards being dealt and the sound of chips being raked across a poker table. But one sound that has yet to appear on their site, and I assume others, is the sound of players fiddling with their chips. If you've ever played poker, or even just seen it played on TV you'll be familiar with players making all sorts of noise as they play around with their stacks when they're not playing a hand. It would be an interesting sound to add to online poker software, as it might annoy your opponents and effect their play. Of course unlike real world poker the online player would have the advantage of being able to turn the sound down if it got too annoying.
Oddly in all the poker I've watched on TV I've never heard anyone complain about players making such noise. Given some of the stuff poker players do complain about it's surprising no one ever seems to blow up at other players for being too noisy.