Here is a hack for Battle City which alters the game-play by giving your tank faster speed and also speeding up the release of enemies on the battlefield at the same time.
BattleCity (Japan).nes - NOINTRO
CRC32: F599A07E
MD5: CD4FE2E78DF0696DBE652F02C19541A1
SHA-1: E1061C9241B06A965FB7845CB951D921ACA010EF
SHA-256: A869AEAD5B6957FC62002FF9636E048CC34BAF0100D629B07DC51AA18F220C0C