Paragon. So much playfield, so few shots. Also, screw that double flipper layout. Also the wimpy, dated sounds do not fit the expectations set by the badass artwork (to be fair, it came out two years too early to have the good Bally sound system). If the artwork wasn't among the best of all time, it'd be firewood to most, I think. Getting stuck playing it in seemingly every tournament has only strengthened my hatred for it.
Metallica. Love the art, it's a good layout, and I'm a fan of the music, but I hate the grindy ruleset. Hit the four things over and over again just to start a mode where you'll accidentally hit a pick target and drain before you can do anything with it. Multiballs are nothing more than ways to grind toward crank-it-up. Then there's Sparky, who his annoying voice and tendency to throw the ball SDTM or down an outlane. This is another game that I'm seemingly stuck playing in every tournament.
Terminator 2. Quite possibly the best example of a great theme gone to waste. With a complete rules re-write that either eliminates the gun completely or at least cuts it down to AC/DC or STTNG levels plus a pinsound board to restore the proper music and dark tone that befits the theme, it could be salvaged. As it is, the load the gun, shoot the gun, rinse and repeat rules make it barely even qualify as playing pinball.