I got a couple houndred favourite songs, so I'll try to limit it to one song per album:
Jesper Kyd - Countdown (Assassin's Creed 3 Brotherhood OST)
Mell - Red Fraction (Black Lagoon Opening theme)
Cara Dillon - Broken Bridges
Chiasm - Isolated
Chiasm - Surrender (took me a while to realize, what the album's overarching theme really is and the realization hit like a brick)
Chiasm - Caffeine Cycle
Covenant - Leviathan
Covenant - Like Tears in Rain
Covenant - Der Leiermann (same music, but very different lyrics)
Covenant - Call the Ships to Port
Covenant - Greater than the Sun
Covenant - Judge of my Domain (essentially the entire album is pure gold, like almost everything from Covenant, but this strikes a particular cord)
Covenant - Leaving Babylon
David Hasselhoff - True Survivor (Kung Fury OST)
Rob Walsh and Tony Pastor - Defenders of the Earth (Opening Theme)
Depeche Mode - Strangelove
Depeche Mode - World in my Eyes
Jackie Chan - Drunken Master (Movie Theme)
Boy George - Felidae (Felidae OST)
Fraktus - Affe sucht Liebe
Game of Thrones - Rains of Castamere
Phil Galdston and John Van Tongeren - No Guts, No Glory (Galaxy Rangers Opening Theme)
FM - Rangers are forever/Rangers ride forever (Galaxy Rangers Outro)
Myles Hunter - Somewhere A Heart (Galaxy Rangers OST)
Kenji Kawai - Making of a Cyborg (Ghost in the Shell 1995 Theme)
Kenji Kawai - Mezame no Hakobune (Ghost in the Shell 2: Innocence Theme)
He-Man and the Masters of the Universe (Opening Theme)
Highway Superstar - Hunters (ft. Sunglasses Kid & Honey Colonna)
In Extremo - Liam
Irfan - Hagia Sophia
Masaki Endo - Kaiketsu Zorro/The Legend of Zorro (Opening Theme)
Kraftwerk - Computer Love
Angela - Knights of Sidonia (Opening Theme)
Marty Simon - Yo-A-O/Fight Song of the Brunnen G/End of the Brunnen G (Lexx OST)
Loreena McKennitt - The Old Ways
Loreena McKennitt - The Mystic's Dream (I wonder if anyone will recognize this)
Loreena McKennitt - The Highwayman
Manfred Mann's Earth Band - The Runner
Marlene Dietrich - Lili Marlene
Max Raabe/Comedian Harmonists - Mein kleiner grüner Kaktus
Max Raabe - Kein Schwein ruft mich an
Melodysheep/Charlie Chaplin - Let us all unite (the greatest speech ever done by anyone, married to Melodysheep's simple but emotion-stirring electronic music)
Mila Mar - Djanga
Mila Mar - Was bleibt...
Nightwish - Ocean Soul
Omnia - Morrigan
Origa - Diva
Origa - Aurora
Origa - Inner Universe
Phil Collins - Another Day in Paradise
Kalafina - Magia (Puella Magi Madoka Magica Opening Theme)
Yuki Kajiura - Sis puella magica! (Puella Magi Madoka Magica OST)
Kōtarō Nakagawa - Dive in the Sky (Planetes Opening Theme)
Qntal - Rossinhol
Qntal - Ab Vox d'Angel
Qntal - Name der Rose
Qntal - Vogelfluc
Robocop 1988 Cartoon - Opening Theme (it has spoken lyrics, so it counts
)
Dale Schacker - Saber Rider (English Opening to Sêjûshi Bisumaruku)
Dale Schacker - Colt (it has lyrics and is on CD 2
)
Savlonic - Computer Guy
Savlonic - Hi-Lights
Savlonic/Evangeline D'isco - Sweet
Scandroid - Pro-Bots and the Robophobes
Boa - Duvet (Serial Experiments Lain Opening Theme)
Takayuki Miyauchi - Special Police Winspector/Tokkei Winspector (Opening Theme)
Steam Powered Giraffe - The Stars (Steamworld: Heist OST)
Andreas Waldetoft - Faster than light (feat. Mia Stegmar) (Stellaris OST)
Sting - Englishman in New York
Sting - Shape of my Heart (I should watch Leon again sometime)
Sting - Desert Rose
Susumu Hirasawa - Island Door (Paranesian Circle) (Ruiner OST Version)
Susumu Hirasawa - Island Door (Paranesian Circle) (Live Version)
Teenage Mutant Hero Turtles - German Opening Theme (not the inferior english original)
The Lord of the Rings - Aragorn's Coronation Song (sang by Viggo Mortensen
The Lord of the Rings - Edge of Night (sang by Billy Boyd)
The Lord of the Rings - Lament for Theodred (sang by Miranda Otto)
The Hobbit - The Misty Mountains Cold
The Midnight - Gloria
The Midnight (feat. Nikki Flores) - Jason
The Midnight - Vampires (yes, I am cheating; sue me, but both "The Midnight" and Nikki Flores deserve their spotlight)
The Midnight - Crystaline
The Police - Every Breath you take
Thomas Bergersen - Children of the Sun (feat. Merethe Soltvedt)
Bernhard Hoffer - Silverhawks (Opening Theme)
Bernhard Hoffer - Thundercats (Opening Theme)
Tobias Sammet - Reach Out For The Light
Total War: Attila - Main Theme
Lion - Transformers (Transformers 1986 movie theme)
Stan Bush - The Touch (Transformers 1986 OST)
Stan Bush - Dare (Transformers 1986 OST)
Try^d - Alone
Try^d - The Final Rewind
U2/Brian Enno - One Minute Warning (if you are old enough to remember, but never knew which song it was, since it was not on the OST, now you know
)
VNV Nation - Solitary
VNV Nation - Standing
VNV Nation - Beloved
VNV Nation - Homward
VNV Nation - Testament
Warhammer 40k - The Lord Inquisitor
Warhammer 40k - Dawn of War 3 - Announcement Trailer (rappers speak their lyrics as well, so this counts)
Warhammer 40k - Dawn of War 3 - Prophecy of War (yes, I said I cheat occasionally, but you already sued me and I got away, so ha ha]
Weebl - They Shall Not Pass
Wolfsheim - The Sparrows and the Nightingales
Wolfsheim - Leave no Deed undone
Wolfsheim - Heroine she said
Wolfsheim - Underneath the Veil
World Order - Have a nice day
World Order - Have a nice day Shibuya Version
World of Warcraft - Nightsong
World of Warcraft - Warbringers: Jaina
World of Warships - Outbreak of World War
Yellow Magic Orchestra - Technopolis
Yellow Magic Orchestra - Citizens of Science
Yellow Magic Orchestra - The City of Light
Yogscast - Diggy Diggy Hole
Yoko Kanno - Torukia (oh everything from Yoko Kanno, really, but this list is way long enough already)
Zack Hemsey - The Way
I hope you find something that you did not yet know and enjoy it. I'll now go eat something, as it took several hours to write and link this