[SwisherSweet]

pawn Код:

public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
    if(dialogid == 1)
    {
        if(response == 1)
        {
            if(listitem == 0)
            {
                ShowPlayerDialog(playerid, 2, DIALOG_STYLE_LIST, "gCars", "Bikes\nBoats\nCars\nFactionCars\nFlans", "Select", "Close");
            }
            if(listitem == 1)
            {
                ShowPlayerDialog(playerid, 3, DIALOG_STYLE_LIST, "gWeapons", "9mm\ns9mm\nDesert Eagle\nShotgun\nSawoffShotgun\nCombat Shotgun\nUzi\nMp5\nAK-47\nNext Page", "Select", "Close");
            }
        }
    }
    return 1;
}

fixed and tested, you should really learn how to script
the problem was you where doing this

}
showplayerdialog bla bla bla
}
you see the brackets?
it should be like this
{
showplayerdialog
}