This thread has far too many posts in it for such a simple question, caused by a lot of people being wrong about the rules for CCW.
Basically, you have the rulebook (presumably), someone should have given you a reference in the first few posts, you should have read that, and understood how it works, since the rules are pretty damn easy to understand.
There are 3 kinds of Close Combat Weapons.
Standard, which confer no special bonuses, just your base S/I/A etc. All Pistols count as a standard CCW.
Special, which confer some kind of special bonus, these include Power Weapons, poisoned weapons, Whichblades, etc. Most of these are specific to a codex.
And then there's the 'heavy' weapons, which are like special weapons, but cannot be used in combination with a CCW of a different type. Note that they aren't necessarily heavy, but it's just a convenient label for this explanation. These include Power Fists, Lightning Claws, and Thunder Hammers; not exclusively, there are codex-specific ones as well.
There are two 'sizes' of weapons.
1-handed: These can be used in combination with another CCW to grant a bonus attack in melee (not in the profile of the model, you add it on to that).
2-handed: These cannot be used in combination with another CCW, you cannot get the bonus attack for having 2CCW if you're using one of these.
The rules for gaining the bonus attack are as follows.
If you have 2 standard CCW, you gain the bonus attack.
If you have 1 standard and 1 special weapon, you gain the bonus attack.
If you have 2 of the same special weapon, you gain the bonus attack, but you would never actually do this as an option (since it's a waste of points, a pistol does just as well).
If you have 2 different special or heavy weapons, you cannot gain the bonus attack, even if you have a spare CCW; this is a penalty for having so many fancy gadgets, in a way.
A heavy weapon can never be used to gain the bonus attack unless you have 2 of the same heavy weapon, like a pair of Lightning Claws, or a pair of Power Fists (like Shrike and Calgar, respectively).
While writing this, I realised that Calgar technically doesn't get the bonus for having 2 fists, because he also has a Power Sword, and so he has two different special weapons, preventing him from gaining the 2CCW bonus.
LOL, NICE ONE GW!