[Arkshine]

Here an optimized version of your current plugin.

• Use a swith() when you can. Instead using several if() in the forward, it's better to use a switch in such case.
• No need to create several variables 'r', 'g', 'b', use random_num() directly in the fm_set_rendering() function.
• It's more readable to write the defined name 'PLUGIN_HANDLED', 'FMRES_IGNORED', etc.. instead of writing its value.
• cmd_access ( id, level, cid, 2 ) : The correct value is 2 because you have to count the command + the argument, so 2.
• In your plugin/case, no need to return something in each 'case:'. It's more readable to remove them.
• You have forget to retrieve the mode value passed into the command.
• Since you're using one function from fakemeta_util, just copy it into your plugin.
• You have missed the mode value into the command function.
• Like connor said, fun is not used, remove it.
• (Optionnal) : Since fakemeta is using, you can use the player's private data to retrieve the team value. Then you can remove cstrike requirement.

PHP Code:

 
    #include <amxmodx>
    #include <amxmisc>
    #include <fakemeta>

    new gi_Mode;
    new gi_MaxClients;

    enum
    {
        CS_TEAM_T = 1,
        CS_TEAM_CT
    }

    #define OFFSET_TEAM 114
    #define cs_get_user_team(%1)  get_pdata_int( %1, OFFSET_TEAM )

    public plugin_init ()
    {
        register_plugin ( "wp_glow", "0.2a", "Radiance" );

        register_forward ( FM_SetModel, "fw_model" );
        register_concmd ( "amx_wpglow", "cmd_wpglow", ADMIN_LEVEL_A, "cmd_wpglow <1|2|3> : switches wpglow modes" );
    }

    public plugin_cfg ()
    {
        gi_MaxClients = global_get ( glb_maxClients );
    }

    public cmd_wpglow ( id, level, cid )
    {
        if ( !cmd_access ( id, level, cid, 2 ) )
        {
            return PLUGIN_HANDLED;
        }

        new s_Arg[ 2 ];
        read_argv ( 1, s_Arg, sizeof s_Arg - 1 );
        
        gi_Mode = str_to_num ( s_Arg );

        switch ( gi_Mode )
        {
            case 1  : client_print ( id, print_console, "%s", "[AMXX] wp_glow switched to <team mode>." );
            case 2  : client_print ( id, print_console, "%s", "[AMXX] wp_glow switched to <random mode>." );
            default : client_print ( id, print_console, "%s", "[AMXX] wp_glow disabled." );
        }

        return PLUGIN_HANDLED;
    }

    public fw_model ( i_Ent,  const s_Model[] )
    {
        static id;
        id = pev ( i_Ent, pev_owner );

        if ( !( 1 <= id <= gi_MaxClients ) )
        {
            return FMRES_IGNORED;
        }

        switch ( gi_Mode )
        {
            case 1 :
            {
                switch ( cs_get_user_team ( id ) )
                {
                    case CS_TEAM_T  : fm_set_rendering ( i_Ent, kRenderFxGlowShell, 255, 0, 0, kRenderNormal, 10 );
                    case CS_TEAM_CT : fm_set_rendering ( i_Ent, kRenderFxGlowShell, 0, 0, 255, kRenderNormal, 10 );
                }
            }
            case 2 :
            {
                fm_set_rendering( i_Ent, kRenderFxGlowShell, random_num( 1,255 ), random_num( 1, 255 ), random_num( 1, 255 ), kRenderNormal, 10 );
            }
        }

        return FMRES_IGNORED;
    }

    fm_set_rendering ( i_Ent, i_Fx = kRenderFxNone, i_R = 0, i_G = 0, i_B = 0, i_Render = kRenderNormal, i_Amount = 16 )
    {
        static Float:vf_RenderColor[3];

        vf_RenderColor[ 0 ] = float( i_R );
        vf_RenderColor[ 1 ] = float( i_G );
        vf_RenderColor[ 2 ] = float( i_B );

        set_pev ( i_Ent, pev_renderfx   , i_Fx );
        set_pev ( i_Ent, pev_rendercolor, vf_RenderColor );
        set_pev ( i_Ent, pev_rendermode , i_Render );
        set_pev ( i_Ent, pev_renderamt  , float ( i_Amount ) );
    }