* MARCEL MARCEAU (Sylvia and Danny Kaye Playhouse):This small theater, connected to Hunter College, scored a coup with their week-long engagement of legendary French mime Marcel Marceau, performing his first New York engagement in 12 years, and his first performance with a company in the city since 1961. Marceau, at 72, demonstrated that he is still a master at an art form he single-handedly popularized (but that in recent years has been held in derision). The evening consisted of two parts: The first half included solo pieces featuring his signature character, Bip, while the second half had Marceau and his young company performing a silent adaptation of Nikolai Gogol's ''The Overcoat.''
* MARATHON '95 (Ensemble Studio Theatre): This is the 18th-annual edition of one of this country's most important festivals of one-act plays. Composed of three separate programs spaced out over the next six weeks, Series A (through this weekend) includes a new play by Arthur Miller, as well as a previously unperformed (and newly discovered) work by Thorton Wilder. Series B (May 17-28) and C (May 31-June 11) include new plays by David Mamet and Craig Lucas, among others.
* THE MOUNTAIN GIANTS (Brooklyn Academy of Music): Giorgio Strehler is one of the world's most acclaimed directors, but his work rarely reaches our shores. BAM, which specializes in presenting international theater productions, has rectified that with their recent import of his company's production of Luigi Pirandello's last, unfinished work. Unfortunately, this talky, problematic play (performed in Italian, with simultaneous translation) received a listless, murky treatment here that belied its director's reputation. Although there are striking moments, and a highly effective climax, the production is a lugubrious experience.