[Zoopaman]

Yay I finally have done it! Inspired by this, I made a *******-style PM system (but you can actually make a real SA:MP ******* with this )

Syntax: "@name/id message" or "@ name/id message" - both work (I haven't tested it with names w/ spaces tho).

Ok I hope I don't miss a part of the code :P And pls don't dis this code because even I'm quite surprised it works, since it came to me while daydreaming :P

So here we go.
Above all:

pawn Code:

forward OnPlayerAtCmd(playerid, cmdtext[]);

in OnPlayerText:

pawn Code:

if(text[0] == '@') {OnPlayerAtCmd(playerid, text[1]); return 0;}

out of callbacks:

pawn Code:

public OnPlayerAtCmd(playerid, cmdtext[])
{
    new idx;
    new string[128];
    new sendername[MAX_PLAYER_NAME];
    new giveplayer[MAX_PLAYER_NAME];
    new cmd[128];
    new tmp[128];
    new giveplayerid;
    cmd[idx] = cmdtext[0]; // this is important - it's what lets you *not* have the whole command and enter the name right after '@'
//The rest except the one above line is pretty much usual PM stuff. This sample is from GodFather (sorry, haters :))
//Also, I'm not sure, but I think that [idx] and [0] can be different. I tried replacing [0] with [1] and [2], but no change whatsoever.
    tmp = strtok(cmdtext, idx);
    if(!strlen(tmp))
    {
        SendClientMessage(playerid, COL_HELP, "USAGE: @[Player ID/Name] [Message]");
        return 1;
    }
    giveplayerid = ReturnUser(tmp);
    if (IsPlayerConnected(giveplayerid))
    {
        GetPlayerName(playerid, sendername, sizeof(sendername));
        GetPlayerName(giveplayerid, giveplayer, sizeof(giveplayer));
        new length = strlen(cmdtext);
        while ((idx < length) && (cmdtext[idx] <= ' '))
        {
            idx++;
        }
        new offset = idx;
        new result[64];
        while ((idx < length) && ((idx - offset) < (sizeof(result) - 1)))
        {
            result[idx - offset] = cmdtext[idx];
            idx++;
        }
        result[idx - offset] = EOS;
        if(!strlen(result))
        {
            SendClientMessage(playerid, COL_HELP, "USAGE: @[Player ID/Name] [Message]");
            return 1;
        }
        format(string, sizeof(string), "New reply from %s (ID: %d): '%s'", sendername, playerid, (result));
        SendClientMessage(giveplayerid, COL_REPLY, string);
        return 1;
    } else {
        SendClientMessage(giveplayerid, COL_ERROR, "Recipient not online");
    }
    return 1;
}

Feel free to use it and add parameters and IsPlayerConnected's and whatever