Highlander (The story of immortal MechWarriors whose 'Mechs can only be brought down by destroying their heads. The main character, obviously, pilots a Highlander.)
Highlander II (Well-panned sequel which "reveals" the immortal MechWarriors are either aliens from a distant part of the galaxy who only have immortality in the Inner Sphere, or time-travelers, depending on which cut of the film you watch. Also, the otherwise pitch-perfect villain, despite being named "Katana," pilots an Atlas, probably in an effort to make him seem more intimidating, and the title character spends most of the film piloting an UrbanMech.
Highlander III (Okay sequel, despite it giving the villain magical powers. At least it gives the Highlander his Highlander.)
Highlander: EndBattle (Taking a character from the popular spin-off TV show and pitting him against the character from the movies [whose actor has gotten too old to believably portray an immortal anymore] and pitting them against a villain with surprise backstory with both of them.)
Highlander: Search for Vengeance (Kurita-produced animated spin-off set in a post-apocalyptic Inner Sphere. Far better than you'd think it would be, given that set-up, premise, and the generally poor track record the film series has had. The first villain pilots a LumberMech, of all things, but works it surprisingly well!)
Highlander: The Source (All around bad film featuring a villain in an Atlas that runs like a Locust, deprives the immortals of their Mech-boosting power, doesn't feature a Highlander 'Mech anywhere, and attempts to explain Immortals and where they come from. Ultimately fails.)