Zombie Games:

• Dead Island / Riptide
• Dead Rising 2 / Off the Record
• Day Z
• Operation Raccoon City
• Resident Evil 6 (it isn't anything like the others, that's why it's here)

Open World:

• STALKER: Call of Pripyat
• Far Cry 3 / Blood Dragon
• Dead Rising 2 / Off the Record
• Day Z
• Dead Island / Riptide
• Cube World
• Dark Souls (more Metroidvania than true open world)

Hm....Resident Evil? IDK.. also, isn't Day Z a mod? If it is, then a mod for what game? Tried Dead Rising, kinda fun, but not my style, I just love to kill around zombie, and I hate those escort missions!
Dead Island? Haven't tried it yet.

Cube World? Isn't still on beta? Will wait for the 1.0 release.
Already tried Dark Souls, meh, good game.
Haven't tried Stalker
I REALLY want to play Far Cry 3...will find the time to buy it.

Day Z is a free mod for ARMA 2: Combined Operations, although I wouldn't recommend buying ARMA 2 just for it. Apparently it's going to go to a standalone release soon so I'd wait till then.

Resident Evil 6 is a lot more action-oriented than the previous games, even more so than RE5. I would not recommend playing it without a friend for co-op though. But it certainly fits the "rampant zombie killing" description, especially in The Mercenaries.

Dead Island shares a lot in common with Borderlands if you're into that - open world, "randomly" generated weapons and level up mechanics with skill trees for different characters who all focus on different weapon classes. Much more melee oriented than Borderlands though.
Riptide and the original Dead Island are very similar so since the first is cheaper (and currently on Humble Bundle if you pay more than $5.24) then I would recommend that instead.
If you like to just run around smashing zombies then that is definitely an option in this game.

STALKER: Call of Pripyat is the third game in the series and my personal favourite. Although not truly open world, it features 3 very, very large maps that you are free to explore as you chose. No levels and RPG mechanics really - your skills come down to your equipment and skill with a mouse and keyboard. It's pretty hard, especially if you're new to the series.
It's set in post-Chernobyl Disaster Ukraine, so has the whole post-apocalypse feel to it - sorta comparable to Fallout but less humorous.

Also if you choose to buy that Humble Bundle you'll also get a bunch of other games including Saints Row 2 & 3. Then again I don't know if you were after console games or PC so perhaps that won't be an option.

Try PewDiePie games

Project Zomboid is one hell of a game, good shit..
If you're into this survival aspect and not the run and gun type of game.

A free fps or even tps where you can customize what your character wears and his guns, etc.
If there are some good paid ones though I will be willing to pay. I however do not want a DEAD game like Crime Craft.

APB Reloaded is the only game that comes to mind that fits all those criteria that also isn't TF2.
I haven't played it myself, and I've heard it isn't very good for a number of reasons (I vaguely remember Pay2Win being one of them...)

Steam name- DogFromHome
Playing many geims.
And if you want BF3, then here's my Origin- DogFromHome

I would like a fighting ragdoll that people actually can control than drag them and crap

Rag Doll Kung Fu is pretty close to what you're after here.
It's a bit tricky to get used to, but good fun once you do.