Depends on mission and situation. If your mission is town, and you suppose to kill it alone of with few friendlies, then:
110g2. It is not fast, but even in agressive environment you can survive long enough. With heavy gun load can get town alone, and can still kill couple of enemy fighters.
a20. Still need some time in this plane, but I think it is a good one is a calm places, or in packs.
Tiffie. My favorite ground attacker, but better get couple friends with you; tiffie can't get the whole town alone with its load.
p38. Very good attacker with heavy rocket/eggs load and good guns/ammo. Can climb, and carry it fast to target, which is good too.
p47d30. Has eggs/rocket punch close to a20, and more .50s. Takes forever to climb it while heavy though.
Hogs. D is not bad as a jabo, but C is the real leader. Eggs, rockets, 4 hispanos, and lot of ammunition. It is perked though.