[MikeJS]

Either

PHP Code:

#pragma semicolon 1
#include <sourcemod>
public OnPluginStart() {
    new Handle:cvar = FindConVar("host_timescale");
    SetConVarFlags(cvar, GetConVarFlags(cvar)&~FCVAR_CHEAT);
} 


or

PHP Code:

#pragma semicolon 1
#include <sourcemod>
#define PLUGIN_VERSION "1.0"
public OnPluginStart() {
    LoadTranslations("common.phrases");
    RegAdminCmd("sm_scvar", Command_scvar, ADMFLAG_GENERIC, "Usage: sm_scvar <name/#userid> <cvar> <value>");
}
public Action:Command_scvar(client, args) {
    if(args==3) {
        decl String:arg1[64];
        GetCmdArg(1, arg1, sizeof(arg1));
        new targ = FindTarget(0, arg1, false, false);
        if(targ!=-1) {
            decl String:arg2[64], String:arg3[64];
            GetCmdArg(2, arg2, sizeof(arg2));
            GetCmdArg(3, arg3, sizeof(arg3));
            SendConVarValue(targ, FindConVar(arg2), arg3);
            ReplyToCommand(client, "[SM] Sent %s = %s to %N.", arg2, arg3, targ);
        }
    } else {
        ReplyToCommand(client, "[SM] Usage: sm_scvar <name/#userid> <cvar> <value>");
    }
    return Plugin_Handled;
} 


"sm_scvar player sv_cheats 1 then "sm_scvar player host_timescale x".

If you're doing it to get unlocks in TF2, neither of them work.