Trojan by Capcom, original arcade release in 1986 and ported a year later to the Famicom (and the following year, the NES).
The early days of the NES brought with it a wave of memorable titles. Trojan was a decent effort, but ultimately one of the more forgettable ones, released in a time when Konami was 3rd part king and Capcom was still finding its footing.
A capable "walk to the right" hack and slash game, Trojan took a cue from several existing games (such as Capcom's own Ghosts 'n Goblins) but simplified the platforming elements dramatically, making for more straightforward (if vanilla) gameplay. The arcade version executed this nicely, with large characters, multiplane parallax scrolling and well-animated characters. Sadly, though the NES conversion sported some nice detailed graphics, the less-fleshed-out gameplay stuck out on a home system and without the upgraded visuals to match the arcade's effort, it made less of an impression.
Even so, the game had merit. Solid gameplay, decent music, and appropriate gameplay control, Trojan put the genre through its paces and included an interesting "sword and shield" mechanic (or gimmick) which, if more well-implemented, could have gone a long way towards giving Capcom their own capable Castlevania at the time.
Instead, the NES featured a 1-on-1 "sub-mode" where 2 players could hack away at one another. Nothing fancy, but you didn't really see many games like this (and genuine 2-player simultaneous games on NES were the exception rather than the rule, in many cases). Trojan turned out nice, and many remember it for it's difficulty and intriguing themes - but ultimately, just another game that fell by the wayside, and yet it is one that would be interesting to revive today. You gotta give it some love for the interesting Simon Bisley meets Gustav Klimpt boxart however. Bravo!