LITTLE SHOP OF HORRORS - Musical comedy about, yes, a big and hungry houseplant that likes to gobble up humans. The first half is yucky but funny, in a tacky sort of way; the rest is repetitious. Based on a zany Roger Corman horror flick and a popular Off Broadway show of the same title, and featuring a lively music score in the high doo-wop style. Directed by master puppeteer Frank Oz. (Rated PG-13) MISS MARY - A proper English governess takes a position with an aristocratic Buenos Aires family, and their relationship mirrors the changes in Argentinian life and politics over a period of several years. A complex and thoughtful film, but low on energy. Directed by Mar'ia Luisa Bemberg, who wrote the screenplay with Jorge Goldenberg. (Rated R) NO MERCY - A cop from Chicago slogs through the swamps and saloons of Lousiana on the track of a psychopath who killed his partner. Grim going. Richard Pearce directed. (Rated R) NUTCRACKER - Lively rendition of the classic Tchaikovsky ballet, with an unusually large amount of plot material from E.T.A. Hoffmann's original story. Carroll Ballard directed the movie, which was designed by Maurice Sendak and choreographed by Kent Stowell, whose Pacific Northwest Ballet is the collective star of the show. While the production sets no high new standards for the dance-film genre, it's always perky and sometimes very inventive. (Rated G) PLATOON - Filmmaker and Vietnam veteran Oliver Stone tries ambitiously to capture the full horror and frenzy of combat in Southeast Asia, but his technical skill outstrips his insight. The result is just another war movie, bigger and bloodier than most, but less hysterical than ``Salvador,'' the last picture Stone wrote and directed. (Rated R) STAR TREK IV: THE VOYAGE HOME - If this keeps up, we'll have more Trekkie film sequels than original TV episodes. And that's fine if they're all as charming as this one. The crew members of the spaceship Enterprise time-travel to 1986 in search of some humpbacked whales, which they need to solve a 23rd-century crisis. Like interstellar cousins of Crocodile Dundee, they hilariously grope their way through today's San Francisco, finding each aspect of the '80s urban scene more inexplicable than the last. In comparison with a ``Star Wars'' or Indiana Jones hit, the visual humor is refreshingly gentle and the dialogue is witty, wistful, and even wise at times. Leonard Nimoy, who plays his perennial role of Spock with ease and assurance, also directed. (Rated PG) TANGOS: THE EXILE OF GARDEL - Through song, dance, and drama, this stunningly original film traces the experiences of several Argentinian performers and intellectuals living in Paris after the 1976 military coup in their own country. Directed by Fernando E. Solanas, who has mellowed in mood but lost no political fervor in the 18 years since his daunting documentary ``Hour of the Furnaces'' was released. The bewitching music is by Astor Piazzolla, the captivating cinematography by Felix Monti. (Not rated) RATINGS: Films with ratings other than G may contain varying degrees of vulgar language, nudity, sex, and violence.