Do I need a CPU fan for gaming?

The default cooler is going to be loud and it's not good for overclocking. If you want quiet then get a nice big 120mm cooler and let the BIOS control the fan speed. If your overclocking though, the board will of course have to increase the fan speed which may make some noise simply from the air turbulence ^_^

Maybe I will overclock if the games wont run properly on my native 1920x1080 resolution. But even then, the default box fan will be enough?

Yes very necessary or you will be meeting Mr. Reboot right in the middle of some serious action on your PC if you do not get a CPU fan. After market CPU fan is extremely recommended if you plan to OC or play games on high grafix settings.

Might i suggest some Thermal paste Artic Silver 5 to ensure lower cpu temps also. very good and affordable b4 you put on that CPU fan.

The stock fan will be enough for light overclocking, assuming your case ventilation is good.

Some of the best CPU coolers are nearly silent, but they are expensive ($90 or so). Noctua NH-D14 or Thermalright Silver Arrow are two of those.

My case is coolermaster elite 430. People told me its pretty good.

It's a good budget case but needs fans added because it only comes with one i could be wrong.
Ideally you want 3 120mm fans in that case for good basic airflow.
1 front intake/1 rear exhaust/1 top exhaust = for starters
I know it has an additional 120mm top mount and a side panel mount and some bottoms.
I would start with 3x120mm fans in the positions i indicated.
You could add an aftermarket cpu cooler but until the case airflow is addressed it would perform less then ideal imho.

Thanks for the help, but I have one more question. Does the X4 Phenom 955 BE come with a default fan from AMD? Or does it have no fan? Because if it doesn't have one, then the Arctic Cooling Alpine Pro would be better than nothing, IMO.

I'm not familiar with the Alpine Pro so I did a google search, seems to only handle 95W processors, probably wouldn't handle cooling a 955 at stock speeds, much less any attempt to overclock.

The cooler that comes with AMD's higher end chips including the 955 is much better, it's even got copper heat pipes and competes well with most coolers in the $20 range. Only downside is it uses a really high rpm fan making for a lot of noise.

If you try to run your PC without any CPU cooling at all, you're going to be buying a new CPU for yourself, because I can almost guarentee you that something will get fried. As long as you didn't buy the OEM version, the 955 comes with a decent heatsink/fan.

Oh ok. So yeah, the stock one is much better. I'll try to improve the airflow then, thank you  

Wait... Whats an OEM version??? How do I know if I didnt buy one? I'm buying from here, if it helps: http://www.mifcom.de/product/444/1/high-performance-gam...

An OEM version doesn't include a HSF, or a 3yr warranty, it's the cpu only.

No worries a custom pre-built will include the HSF and 3yr warranty.
Unless you choose a different HS.

Ok thanks then