Z-TACK / Bomb / Atari 2600

Kind of a twist on Space Invaders, Z-Tack has you as a fat alien spacecraft bombing the shit out of increasingly complex alien civilizations entrenched in tunnels. They resist by having largely useless cannons that fire straight up here and there, there's also Skull Mines that randomly appear, and in later levels turn into some sort of Bore Worm thing that charges sideways. None of this is ever very effective in stopping your annihilation of their civilization, however - the game is just too easy, repetitive and dull.