[Kevln]

I'd do it like this:

pawn Код:

switch(random(100))
{
    case 0: // 1 percent chance
    default: // 99 percent chance
}

Another example of 5 & 95 percent:

pawn Код:

switch(random(100))
{
    case 0..4: // 5 percent chance
    default: // 95 percent chance
}