hehe same project that i working on,
hope ur worx without sv_cheats 1
here´s my code
only working with "sv_cheats 1" 
PHP Code:
//**(my=[copy/snip from aka matrix bullettime [V0gelz] )
public Action:Event_Infected_Death(Handle:event, const String:name[], bool:dontBroadcast)
{
if (GetConVarInt(n8matrixhead) == 1)
{
new headshot = GetEventInt(event, "headshot"); //headshot only
if(headshot == 1)
{
new n8mrando = GetRandomInt(1,5);
if((n8mrando == 3) && (n8mtrixTimer == INVALID_HANDLE)) n8mmatrix();
}
}
}
n8mmatrix()
{
if (n8mtrixTimer == INVALID_HANDLE)
{
CreateTimer(0.1, count_15);
CreateTimer(0.2, count_14);
CreateTimer(0.3, count_13);
CreateTimer(0.4, count_12);
CreateTimer(0.6, count_11);
CreateTimer(1.0, count_10);
CreateTimer(1.2, count_9);
CreateTimer(1.5, count_8);
CreateTimer(1.8, count_7);
CreateTimer(2.1, count_6);
CreateTimer(2.3, count_5);
CreateTimer(2.5, count_4);
CreateTimer(3.0, count_3);
CreateTimer(3.5, count_2);
CreateTimer(4.0, count_1);
//CreateTimer(4.0, count_0); //cooldown timer [n8mtrixTimer]
//PrintToChatAll("\x04[test]\x01 an"); //debug
}
}
public Action:count_1(Handle:timer){
ServerCommand("host_timescale 1.0");
n8mtrixTimer = INVALID_HANDLE;
}
public Action:count_2(Handle:timer) ServerCommand("host_timescale 0.9");
public Action:count_3(Handle:timer) ServerCommand("host_timescale 0.8");
public Action:count_4(Handle:timer) ServerCommand("host_timescale 0.7");
public Action:count_5(Handle:timer) ServerCommand("host_timescale 0.6");
public Action:count_6(Handle:timer) ServerCommand("host_timescale 0.5");
public Action:count_7(Handle:timer) ServerCommand("host_timescale 0.4");
public Action:count_8(Handle:timer) ServerCommand("host_timescale 0.3");
public Action:count_9(Handle:timer) ServerCommand("host_timescale 0.3");
public Action:count_10(Handle:timer) ServerCommand("host_timescale 0.4");
public Action:count_11(Handle:timer) ServerCommand("host_timescale 0.5");
public Action:count_12(Handle:timer) ServerCommand("host_timescale 0.6");
public Action:count_13(Handle:timer) ServerCommand("host_timescale 0.7");
public Action:count_14(Handle:timer) ServerCommand("host_timescale 0.8");
public Action:count_15(Handle:timer) ServerCommand("host_timescale 0.9");