Put this after AtRoundStart
---------------------------

bool isValidEnt( cl_entity_s *ent ){
 if( ent && ( ent != pEngfuncs->GetLocalPlayer( ) ) && !( ent->curstate.effects & EF_NODRAW ) && ent->player && !ent->curstate.spectator && ent->curstate.solid && !( ent->curstate.messagenum < pEngfuncs->GetLocalPlayer( )->curstate.messagenum ) ){
  return true;
 }
 else{
  return false;
 }
}

void PlayerBoxEsp()
{
float drawhere[2];
vec3_t vecScreen;
int espr,espg,espb; // For teh Weapon
espr = 255;
espg = 0;
espb = 0;
char nbuf[1024];
cl_entity_t *ent, *pLocal = pEngfuncs->GetLocalPlayer();
hud_player_info_t pinfo;
// Lets begin a loop
 for(int i = 0; i < 33; i++)
{
  if(i == pLocal->index) continue;
  cl_entity_s *ent = pEngfuncs->GetEntityByIndex(i);
  pEngfuncs->pfnGetPlayerInfo(i, &pinfo);
  if(ent != NULL && isValidEnt(ent)/*Credits to tabris*/)
{

   if(CalcScreen(ent->origin,vecScreen))
     sprintf(nbuf,"%s",pinfo.name);
     float drawhere[2];
     CalcScreen(ent->origin, drawhere);
{
     sprintf(nbuf,"%s",pinfo.name);
     CalcScreen(ent->origin, drawhere);
     int namelen;
     namelen = strlen(nbuf);
     if( strstr( pinfo.model, "arctic" ) || strstr( pinfo.model, "guerilla" ) || strstr( pinfo.model, "leet" ) || strstr( pinfo.model, "militia" ) || strstr( pinfo.model, "terror" ) ) {
      espr = 255;
      espg = 40;
      espb = 40;
     }
     else if( strstr( pinfo.model, "gign" ) || strstr( pinfo.model, "gsg9" ) || strstr( pinfo.model, "sas" ) || strstr( pinfo.model, "urban" ) || strstr( pinfo.model, "spetsnaz" ) || strstr( pinfo.model, "vip" ) ) {
      espr = 40;
      espg = 80;
      espb = 255;
     }
     if (isValidEnt(ent)==true)
     {
                    pEngfuncs->pfnFillRGBA(drawhere[0] - 10, drawhere[1] - 10, 20,2,espr,espg,espb,200);
                    pEngfuncs->pfnFillRGBA(drawhere[0] - 10, drawhere[1] - 10, 2,20,espr,espg,espb,200);
                    pEngfuncs->pfnFillRGBA(drawhere[0] - 10, drawhere[1] + 9, 20,2,espr,espg,espb,200);
                    pEngfuncs->pfnFillRGBA(drawhere[0] + 9, drawhere[1] - 10, 2,20,espr,espg,espb,200);
     }
//     DrawHudString(drawhere[0] - namelen * 2, drawhere[1] - 14, /*er*/255, /*eg*/255, /*eb*/255, nbuf);
     }
   }
}
}

------------------------
this in DrawOnHud
------------------------

 if(cvar.box)
 {
  PlayerBoxEsp();
 }

Box ESP tut by V0gelz, this is just c+p easy to use

credits: me, h1web ...