Jeez...that's not easy because there are so many.
Roundabout and Tom Sawyer are good ones. Others that come to mind without too much thinking:
Black Sabbath: Iron Man, Heaven and Hell
Dio: Caught in the Middle
DT: The Killing Hand, Only a Matter of Time, Metropolis I, Learning to Live, Scarred, Overture 1928, About to Crash Reprise, Stream of Consciousness, Panic Attack, Constant Motion, Breaking All Illusions
Fates Warning: Traveler in Time, Fata Morgana, Quietus, Acquiescence, Part of the Machine, Leave the Past Behind, Monument, APSOG I and XI, And Yet It Moves
Genesis: Duke's Travels, No Reply At All
Helloween: Halloween, I Want Out, Keeper of the Seven Keys, For Whom the Bell Tolls, Creeping Death, Battery, Blackened
Ozzy: Crazy Train, Over the Mountain, SATO, Diary of a Madman
Queensryche: Queen of the Reich, Deliverance, NM156, Speak, Eyes of a Stranger, Resistance
Rush: WAY too many to name, but at least the following: By-Tor, Bastille Day, 2112 Overture, AFtK, Hemispheres, La Villa, Spirit of Radio, Natural Science, YYZ, Limelight, Subdivisions
Styx: Suite Madame Blue, Put Me On, The Grand Illusion, Great White Hope, Renegade, The Best of Times
Triumph: Hot Time (In This City Tonight), Too Much Thinking
UFO: Rock Bottom, This Kid's, Love to Love
The Who: Baba O'Reilly, Won't Get Fooled Again, The Real Me
Yes: Yours Is No Disgrace, Starship Trooper, Heart of the Sunrise, The Revealing Science of God, Awaken, Machine Messiah
Iron Maiden: The Phantom of the Opera, Wrathchild, The Prisoner, TNotB, Hallowed Be Thy Name, Where Eagles Dare, Still Life, To Tame a Land, Aces High, Powerslave, SSoaSS
Judas Priest: Victim of Changes, The Ripper, Desert Plains, The Hellion/Electric Eye (which is probably cheating, but still), The Sentinel, Painkiller
Metallica: Anesthesia, Seek & Destroy,