Almost looks like an Arcus to me.

I don't think so. The pistol grip does look similar, and it takes Uzi-style mags, but everything else is off, starting with the fact that the mag release on the mystery SMG is located on the back, not the side, of the mag well. Plus, the gun in "Smallville" is clearly an open-bolt design with the bolt located on top of the receiver.

I found a Brazilian subgun which has a similar-looking magwell, which is called the BSM/9 M3. Here's a picture of it:

http://www.imfdb.org/images/2/28/Scr...._16_00.32.jpg

I don't think this is necessarily the same gun, but it might just be the basis of the Cylon SMG seen in "Battlestar Galactica" and also the same episode of "Smallville":

http://www.imfdb.org/images/a/a7/Gun_Cylon_stunt.jpg
http://www.imfdb.org/images/f/fb/BsgAP9a.jpg
http://www.imfdb.org/images/a/ae/Clownrobbers6.jpg

It could also be one of the many blank firing only guns made in the 90's, and now made by Voltran/Ekol that resemble the brownings but ain't quite exactly perfect.

What's this gun?
http://i37.tinypic.com/2uiydnb.jpg

Oh damn. Sorry for bothering you guys. I've already found it...
It's Walther P-88 I think.
http://www.aceros-de-hispania.com/im...kel-pistol.jpg

Yup, the safety is on as well.

What's this one?

http://i28.tinypic.com/2ake3j5.jpg

How about this?
http://i48.tinypic.com/wagexi.jpg

Walther P99, if not that a Walther P22.

Some kind of Smith & Wesson, I don't know which one.

This one maybe?
http://i48.tinypic.com/9beog3.png

Negative, it's a Smith & Wesson Model 910. You can tell by the way the front of the slide is cut, as well as the new cutout of the frame.

http://www.galeon.com/armasonline/do...tolas/9101.jpg