This list basically exists because I am occasionally forgetful and need to be able to confirm whether or not I already own something when out in shopping for comics etc.

DC Comics
Absolute Batman Long Halloween
All-Star Batman and Robin PB
Arkham Asylum- Madness HC
Arkham Asylum PB
Arkham Asylum Living Hell PB
Batgirl Greatest Batgirl Stories Ever Told PB
Batman A Death in the Family PB
Batman Anarky PB
Batman Arkham Asylum PB
Batman Batgirl PB
Batman Battle for the Cowl HC
Batman The Black Glove HC
Batman The Black Mirror HC
Batman Broken City PB
Batman Broken Mirror PB
Batman Bruce Wayne Murderer? PB
Batman Cacophony HC
Batman Cataclysm PB
Batman Dark Knight Returns
Batman Dark Knight Strikes Again
Batman Dark Victory PB
Batman Dead to Rights PB
Batman Death and the Maidens PB
Batman Death of the Family HC
Batman Detective Comics Faces of Death
Batman Earth One
Batman Ego and Other Tales PB
Batman Faces
Batman Face the Face PB
Batman Gates of Gotham PB
Batman Going Sane PB
Batman Gotham After Midnight PB
Batman Gotham Underground PB
Batman Harley and Ivy HC
Batman Haunted Knight PB
Batman Heart of Hush HC
Batman Hush Volume 1 PB
Batman Hush Volume 2 PB
Batman Hush Returns PB
Batman Jekyll And Hyde PB
Batman Joker’s Last Laugh PB
Batman Joker’s Asylum Volume 1 PB
Batman Joker’s Asylum Volume 2 PB
Batman Killing Joke HC
Batman Knightfall Volume 1 Broken Bat PB
Batman Knightfall Volume 2 Who Rules the Night PB
Batman Knightfall Volume 3 Knightsend PB
Batman Lovers & Madmen PB
Batman Mad Love and Other Stories HC
Batman No Man’s Land Volume 1 PB
Batman No Man’s Land Volume 2 PB
Batman No Man’s Land Volume 3 PB
Batman No Man’s Land Volume 4 PB
Batman No Man’s Land Volume 5 PB
Batman Private Casebook PB
Batman Return of Bruce Wayne HC
Batman RIP Deluxe Edition HC
Batman Rules of Engagement HC
Batman Secrets PB
Batman Streets of Gotham Hush Money PB
Batman Streets of Gotham House of Hush HC
Batman Streets of Gotham Leviathan HC
Batman Through the Looking Glass HC
Batman Under the Hood 1 PB
Batman Under the Hood 2 PB
Batman War Drums PB
Batman War Games 1 PB
Batman War Games 2 PB
Batman War Games 3 PB
Batman Year 1 PB
Batman Year 2 Two-Face & Scarecrow PB
Batman & Robin- Batman Reborn HC
Batman & Robin- Batman vs Robin HC
Batman & Robin- Batman & Robin Must Die HC
Batman & Robin- Dark Knight vs White Knight HC
Batman and Robin Born to Kill HC
Batman and Son PB
Batman/Joker Switch PB
Birds of Prey- Platinum Flats PB
Catwoman Crime Pays PB
Catwoman Long Road Home PB
Catwoman Trail of the Catwoman PB
Catwoman When in Rome PB
Flashpoint PB
Flashpoint World of Flashpoint featuring Batman PB
Gotham City Sirens Volume 1 PB
Gotham City Sirens Volume 2 PB
Gotham Central Unresolved Targets PB
Greatest Joker Stories Ever Told
Harley Quinn Preludes and Knock Knock Jokes HC
Harley Quinn Welcome to Metropolis PB
Harley Quinn Night and Day PB
Harley Quinn Vengeance Unlimited PB
Harley Quinn Volume 1 Hot in the City PB
Harley Quinn Volume 2 Power Outage PB
Harley Quinn Volume 3 Kiss Kiss Bang Bang PB
Harley Quinn Volume 4 A Call to Arms PB
Harley Quinn Volume 5 The Joker’s Last Laugh HC
Harley Quinn & Power Girl PB
Harley & Ivy PB
Injustice Gods Among Us Year One Complete Collection PB
Injustice Gods Among Us Year Two Complete Collection PB
Joker HC
Joker Greatest Joker Stories Ever Told PB
Joker Death of the Family PB
Joker/Mask PB
JLA Earth 2 HC with Blu-ray/DVD
JLA Salvation Run PB
Red Hood Lost Days PB
Suicide Squad Volume 1 Kicked in the Teeth PB
Suicide Squad Volume 2 Basilisk Rising PB
Suicide Squad Volume 3 Death is for Suckers PB
Suicide Squad Volume 4 Discipline and Punishments PB
Suicide Squad Volume 5 Walled In PB
New Suicide Squad Volume 1 Pure Insanity PB
New Suicide Squad Volume 2 Monsters PB
New Suicide Squad Volume 3 Freedom PB
New Suicide Squad Volume 4 Kill Anything PB
Superman Emperor Joker PB
Superman/Batman Vengeance PB
Zatanna the Mistress of Magic PB

All New Invaders! PB
Amazing Spider-man Edge of Spiderverse PB
Amazing Spider-man Renew Your Vows PB
Avengers Standoff! HC
Bitter March
Bucky Barnes Winter Soldier Volume 1 PB
Bucky Barnes Winter Soldier Volume 2 PB
Captain America Civil War Prelude
Captain America Winter Soldier PB
Captain America Red Menace PB
Batman Death of Captain America PB
Captain America Lives! – Marvel Omnibus
Captain America The Trial of Captain America – Marvel Omnibus
Captain America Return of the Winter Soldier – Marvel Omnibus
Captain America & Bucky Old Wounds PB
Captain America & Bucky: The Life Story of Bucky Barnes HC
Captain America Steve Rogers Volume 1 Hail Hydra PB
Captain America Steve Rogers Volume 2 Trial of Maria Hill PB
Civil War PB
Civil War II- Choosing Sides PB
Civil War II HC
Deadpool Complete Collection Volume 1 PB
Deadpool Max Nutjob PB
Deadpool Soul Hunter PB
Fear Itself PB
Invaders Now
Miss Marvel Volume 1 PB
Original Sin PB
Secret Invasion PB
Spider-Gwen Volume 0 Most Wanted PB
Spider-Gwen Volume 1 Greater Power PB
Spider-Gwen Volume 2 Weapon of Choice PB
Spider-Man/Deadpool Isn’t it Bromantic? PB
Thor Volume 1 PB
Thor & Loki Blood Brother HC
Thunderbolts There is no High Road PB
Vote Loki PB
Winter Soldier Bitter March PB
Winter Soldier Complete Collection PB
Winter Soldier Electric Ghost PB

Other Not necessarily by other companies but fall outside normal continuities
Invader Zim Volume 1
Kick-Ass 2 Prelude Hit-Girl
Kick-Ass 2
Kick-Ass 3
Kingsman Secret Service
Once Upon a Time Shadow of the Queen
Pride, Prejudice and Zombies
Snowpiercer 1 The Escape
V for Vendetta

Injustice Year 3 Part 1 Paperback