Spidey teams up with Red Sonja
Marvel Team-Up (1972 - 1985 1st Series) #79 (March '79) by Chris Claremont and John Byrne is a typically well-done Claremont/Byrne collaboration. When freelance photographer Peter Parker attends the annual Christmas party at the Daily Bugle, he and reporter Charley Snow are sent out to cover a developing story at the Metropolitan Museum of Art. Peter's love interest Mary Jane Watson invites herself along, and when they arrive at the scene a blood-red energy beam lances up from the museum, chilling everybody in the crowd down to the bone. Peter slips away to sneak into the museum as Spider-Man, and Mary Jane (miffed at Pete's oft-repeated disappearing act) enters a side door of the museum she finds unlocked, naturally assuming that Peter went in to investigate and maybe get some photos for the Bugle. Spidey is immediately attacked by some nasty looking mystic entities, and MJ walks around a corner to see Spider-Man getting the life squeezed out of him. Frozen in fear, she notices an ancient sword in a display case beginning to glow. Listening to an inner voice she reaches into the case and grabs the sword, and suddenly she transforms into Red Sonja, warrior woman of the Hyrkanian Steppes. Their mutual foe is none other than Sonja's longtime enemy, evil sorcerer Kulan Gath.
Sonja immediately rushes in and saves Spidey's life, and there's an obvious language barrier between the two heroes. Spider-Man later returns the life-saving favor, but the warrior goddess in the chain-mail bikini isn't very appreciative. :-) When the battle finally ends and Kulan Gath's malignant spirit is banished from a museum guard's body due to a jaw-fracturing punch by Spider-Man, Sonja drops her sword and slowly transforms back to Mary Jane. Pete takes her home and she dismisses the experience to a bad dream.
This premise of Mary Jane's body being borrowed by the spirit of Red Sonja was later revisited in the limited series Spider-Man/Red Sonja (2007) #1 - 5 (Oct. '07 - Feb. '08), a joint venture between Marvel and Dynamite.