Yeah, this is definitely my kind of fps. The only fps game that I ever enjoyed as much was a relatively unheard of mod for Wolfenstein: Enemy Territory which I used to play back around 2007. It was called True Combat Elite. It was pretty much a carbon copy of Insurgency with fewer weapon choices and poorer graphics.
Try playing True Combat: Elite
http://www.truecombatelite.com/index.php?page=tceoverview
It's free, cross platform, and incredibly well thought out. Think of it like CS:S, with no crosshair, but iron sights, and different walking/running mechanics, and the ability to lean left or right.
TCE is as close as you're gonna get. It's alot like Rainbow Six 3.
Here is the downloads page. Look on the forums if you have trouble installing.
I would include True Combat Elite (ET Mod) in that list. It's a really, really great FPS. And it's the only FPS that implements realistic weapon free-aiming.
http://www.truecombatelite.com/
Edit: I've just seen that Red Orchestra 2 also incudes free-aiming :)
TC:E was a fantastic game but it is severely dated. The creator has recently released an alpha version of a newer game called True Combat: CQB which you can find here : http://www.truecombatelite.com/tce.php?page=downloads
I have not played this particular mod, so I can't vouch for it.
Wolfenstein : Enemy Territory is a lot of fun, not a single executable but it's a 200mb download and unpacked about 400mb in total (Of the top of my head) so really easy to share, it's a free game and demands zero gpu power :)
There are some fun mods for it like Jaymod which let you set the gravity & has funmodes like panzer/sniper war. Especially the panzerwars are awesome.
Also check out the total conversion mods True Combat Elite and CQB, they add a CoD-like feel to the game and I really like it.
You can find the downloads here:
The main Dev Coroner came back and started to work on this version. Here's the website http://www.truecombatelite.com/. Not a lot of people playing CQB right now. Mostly because playing one map over and over for almost half a year kind of gets old. But a new map is coming next patch and he might be unlocking the game. So I'm looking forward to that