Stay away from Revolvers if you want a thin gun, with the exception of J-Frames from S&W, they tend to bulge out a bit and only offer 5 shots. If you want slim, stay with an auto.
There are some nice autos out there:
S&W M&P compact in 9MM
Springfield XD 45ACP Compact, has 10 or 13 round magazines.
CZ 83, 12 rounds of 9MM Makarov. It's also steel, affordable, and reliably comfortable.
Kahr, pretty much got going on the 9MMcompacts, they have a nice Single Stack version available in 9MM. Zespectre gave a good listing of their models.
Kel-Tec, makes the thinnest smallest, most compact pistols on the market. However, there are somethings you should know about them. Most Kel-Tecs require some TLC right out of the box to make them reliable. You have to do a "Fluff and Buff" on the feedramp to ensure that ammo will feed reliably that's detailed on this site:
www.ktog.org (Kel-Tec Owner's Group). KT is great in design and ideas, but not the best in execution. However, I do own a P3AT and love the little gun it's less than 3/4 of an inch thick all the way around the handle. If the PF-9 comes out nicely, I am going to buy one.
Taurus: Millenium Pro series, they have versions in 9MM, 40 S&W, and 45ACP.
Anyone else got any ideas? I am kind of fried right now.