I use either the iPod sock, or a Sena leather case. I really don't like how silicon picks up rubbish from the pocket, but oh well!
At the moment I'm using Belkin Sillicon Case but I also used Switcheasy Rebel Serpent, it really protects your phone when you drop it
(which I unfortunately did several times)
I tired silicon and disliked it too. Keeps the phone from sliding into my pants front pocket!
Unfortunately I don't recall the brand but my Silicon case tore so I replaced it with a 2 piece hard Griffin case which the iTouch slides into (sorry don't know the name). I like it cause its smoke/clear in color and has a smooth soft feel. I use a screen protector because the texture/touch feels better to me than without. Guess its all about the feel! LOL
I use the Leather Sleeve for ipod touch from incase
I used the DLO Jam Jacket on my original iPhone 2G and bought it again on day one for my iPhone 3GS. I love it, it's an awesome case with great design and protects your phone to the fullest. I've even thrown my phone out of my car several time a few feet (by accident of course) and it absorbs all impact and my phone is spotless.
I also use the speck candy shell. (black and Yellow) The yellow is now faded, but the phone is well protected. The only complaint I have is that there is a small plastic/rubber cover that rests over the power button, and it is rather difficult to press down which makes taking screenshots and doing hard resets very tedious.