These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Crowning Music of Awesome: Pretty much every game in the series, especially Turrican II. In fact, that game had a live orchestral performance of Turrican II's soundtrack in Leipzig, Germany.
Even Better Sequel: Turrican 2 has bigger worlds, better weapons, improved graphics and possibly the best music.
Game Breaker: In Turrican 3, you can find a secret powerup in the beginning of the second world. This turns your suit gold and you powerups will no longer downgrade if you lose a life. However, getting a Game Over and continuing will lose the suit. This is absent in the original Mega Turrican version.
Wheel mode in Turrican II has no limitations and makes you immune to nearly all forms of damage, making it trivially easy to pass through screen-filling lasers unscathed.
Goddamned Bats: Robot bee hives, especially if you don't have a levelled wide-angle weapon. Also the, well, bats in World 4 of the original, which are hard to hit and constantly spawn clones which spawn more clones.
Porting Disaster: The first two Turrican games suffered from this. The Mega Drive/Genesis port was the most intact, but had clunky controls; The Turbografx-16 had the same clunky controls and also was missing all of world 3 and had a limited soundtrack; and the Game Boy also has a world missing as well as sluggish controls. Turrican II was worse. It was released as Universal Solider as a movie tie-in for the Mega Drive/Genesis and Game Boy. Ouch.
Actually, averted with Turrican 2. "Universal Soldier" plays exactly the same as the original game, just with new graphics and a different story.
Sequelitis: The first two games created by Manfred Trenz are generally considered superior to the sequels that followed without his involvement.
That One Level: World 4 in Turrican is a massive three part maze with creepy ambient sound instead of the Crowning Music of Awesome featured everywhere else. Power-ups are much harder to find than normal, and even if you know where to go, dozens of pixel-perfect (and sometimes entirely illogical) jumps are required to reach the exit. All of the womb levels in the sequels have similar length and difficulty, but the first one took the cake.