Balancing
 

Why not just make the damage proportional to the number of people using it? Have a base damage, and then apply a modifier based on the relative popularity of the weapon. Then everything gets balanced out pretty nicely, and people are encouraged to try all the different options.

You'd probably need to do some tweaking to get it working nicely, and maybe there'd have to be some means by which the players can see the current popularities (else it would be too difficult to know how powerful a given weapon currently is), but still, it doesn't sound like too much work.

On a similar note, you could alter the worlds so that the experience and money rewards are based on the average playercount. Or, for the team-based worlds, make it so that you get more experience if your team is smaller than your opponent's.

Nobody uses combat knife, that'll boost it up enough to make it 2 hits x.x

More people would then use it.
The damage would then be decreased.

This kinda thing balances out over time.

Yeah this is a good idea but you'd constantly see the numbers changing as people try to get a high damage weapon then changing as soon that one is useless, might get sort of annoying.

It's better to make manually modifications to the weapons I guess, sometimes also the frequency / freezeing time need to be modified to make a weapon more interesting, also many weapons have special purposes which cannot easily be detected, also it depends heavenly on the map - on Koth the DH18 is more helpful while chaingun is hard to use because it's more about fights between groups of people. The knife is not meant to be a main weapon, for attack it is better to use muramasa or plasmasabre, but the knife can be used if you are trapped and need some melee weapon quickly.

Agreed, but that can be done independently of the damage calculation.

Well, I am not saying that all weapons would use the same function for determining damage, where popularity is the only variable. Everything would have a base damage that gets modified. For example, a single pistol would start at low damage and maybe it would get more powerful, but even at low popularity it wouldn't be as powerful as an average-popularity shotgun.

So the base damage would be decided by taking into account the weapon's speed, handedness (1h or 2h) and special effects. The balance modification would be relatively minor.

Hm, fair point. Of course, it could be map-specific.

Well, my system would not make it into one. Even with zero popularity, it probably wouldn't get as powerful as the other swords.