[Indarello]

if somebody give weapon which client already can pick up and equip it:
new zweapon = GivePlayerItem(client, "weapon_glock");
if(zweapon != -1 ) EquipPlayerWeapon(i, zweapon);

you will need to clear duplication in this table

g_iMyWeapons = FindSendPropInfo("CBaseCombatCharacter", "m_hMyWeapons");

for (new i = 0; i <= 128; i += 4)
{
	new weaponentity = -1;
	new String:weaponname[32];
	weaponentity = GetEntDataEnt2(client, (g_iMyWeapons + i));
	if ( IsValidEdict(weaponentity) )
	{
		GetEdictClassname(weaponentity, weaponname, sizeof(weaponname));
		PrintToChatAll("[%d][%d][%s]", i, weaponentity, weaponname);
	}
}

So maybe i found a solution for this problem
https://forums.alliedmods.net/showthread.php?t=281687
When :

    if(knife != -1)
    {
        PrintToServer("EquipPlayerWeapon(%N, %i)", client, knife);
        EquipPlayerWeapon(client, knife);
    }

he make duplication in table m_hMyWeapons
This duplication can make server freeze until you restart server manualy

Here is my solution, may not work with grenades:

int zweapon = GivePlayerItem(client, "weapon_glock");
if(zweapon != -1) EquipPlayerWeapon2(client, zweapon);

bool EquipPlayerWeapon2(int client, int weapon)
{
	for (int i = 0; i <= 128; i += 4)
	{
		int weaponentity = -1;
		weaponentity = GetEntDataEnt2(client, (g_iMyWeapons + i));
		if (weaponentity == weapon)
		{
			return false;
		}
	}
	for (int i = 0; i <= 128; i += 4)
	{
		int weaponentity = -1;
		weaponentity = GetEntDataEnt2(client, (g_iMyWeapons + i));
		if (!IsValidEdict(weaponentity))
		{
			SetEntDataEnt2(client, (g_iMyWeapons + i), weapon);
			return true;
		}
	}
	return false;
}