What is a sharp line against the Lion? What is a sharp line for White against the Philidor Lion: 

[FEN ""] 
1.e4 d6 2.d4 Nf6 3.Nc3 Nbd7


with 4...e5

The majority of games seem to be slow positional battles where Black is quite solid.  4.g4 looks interesting, but are there other aggressive ideas?
As you mentioned, 4.g4 is interesting and not as stupid as it may look. If you don't like the positional maneuvering game, I think 4.f4 could be try for you. 

There is one suicidal line that really isn't my taste, but for sure it is aggressive, at least till you get mated. It's 

[FEN ""] 
1.e4 d6 2.d4 Nf6 3.Nc3 e5 4.Nf3 Nbd7 5.Bc4 Be7 6.Ng5 O-O 7.Bxf7+ Rxf7 8.Ne6


even some correspondence player advocated it for white, but I'm not sure I would prefer white's position here. Anyway, good to know such a line exists and is probably not complete nonsense.