4...Nf6 is absolutely fine. 5.Ng5 d5 6.ed5 Qe7+! is a (very small) Black advantage, while on 5.e5 all three possible moves (5...Ne4, 5...Ng4 and 5...d5) are perfectly OK.
The only reason to stay away from 4...Nf6 is avoiding the drawish 5.0-0 Nxe5 6.Re1 d5 7.Bxd5 variation, although even here Black can play for a win if he is willing to take a mild risk.
If you feel Black is OK after something like 4...g6 5.Nxd4 Bg7 6.Nxc6 bc6 7.0-0, the go on. I think I will give it a miss.
1.e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4. Now i have tried all options as 4th move as black like Bb4, Bc5, d6, Nf6 (dont like when Ng5 and even its main line after e5 push, white's e and f pawn makes trouble for black). so now i m going to try surprise move 4....g6 ! That was played by some GMs including 2720 rated Mamedyarov. whats your opinion friends???