McGrath and Gillespie are the best fast bowling combination toady, if not one of the best in the past decade or so, getting up there with the likes of Ambrose-Walsh and Donald-Pollock.
Akthar-Sami.....very lethal pace, but very unpredictable (or their day they can be very destructive)
Hoggard-Harmison.......great combination of pace and swing, just need more experience and need to play in winning team for w little while longer.
Vaas-Zoysa........Vaas is a very good bowler, but Zoysa is very unpredictable, seeing how tall he is he should be bowling a lot faster than he bowls currently (He bowls at around 120-125 Kmph range......thats ridiculous, S.Waugh was bowling quicker than that when he retired!!!!!)
Pathan-Balaji...........the best combination of upcoming young fast bowlers, if they remain injury free than they and continue to imrprove they can take the mantle from McGrath and Gillespie. They both are excellent swing bowlers and very accurate (well Balaji has been a bit off in the Asia cup so far). Pathan is improving rapidly and will only get better with more exposure in Tests and ODI's...