I'm not sure how back they carry in-stock issues, but here are some of my favorites (issue number, and the adventures that make them worth getting):
#29: Ex Libris, Mightier than the Sword
#30: A Wrastle with Bertrum
#34: Isle of the Abbey, The Lady Rose
#35: The Ghost of Mistmoor
#39: The Ulrich Monestary, Legardemain
#41: Old Man Katan and the Mushroom Band
#46: Dovedale, Goblin Fever, Floating Rock
#47: When the Lights Go Out, The Assassin Within
#48: To Bite the Moon, Them Apples
#55: Umbra, Sea Wolf
#60: Shards of the Day, Nemesis
#62: The Rat Trap
#65: The Unkindness of Ravens
#71: Priestly Secrets, Dreadful Vestiges
#72: No Stone Unturned, Deep Trouble in Telthin, Under a Pale Moon, Mistress on the Mere
#75: The Forgotten Man
#77: Wind Chill
#80: Fortune Favors the Dead
#86: Rana Mor