I have read in a comment that quote " There are some chapters that even use Chaos forged weapons against Chaos ", the comment is from this question . Wouldn't the chapters using such weapons be considered heretics for using unclean weapons and machinery(war-machines are weapons, right?). Is this true(the usage of heretical weapons)? And if so, which are those chapters?
Some are, some aren't depends how open they are about it and what they do with said weapons/vehicles
Relictors (Fire Claws)
When fighting a Champion of Tzeentch, Librarian Decario used its own daemon weapon against it to easily destroy it, this was after power weapons and terminators proved useless against the Champion. After this they believed that daemon weapons could be used to fight chaos and went around collecting all daemon artifacts they could find.
Eventually they were found out by the Imperium and group of Inquisitors and other Chapter Masters forced them to hand over all the artifacts to be destroyed and sent the Relictors on a century-long penance crusade.
They survived this crusade and rebuilt their chapter but carried on their collecting in secret. This collecting eventually culminated with a Relictors raid on the remote Diamedes Archive where the Space Marines destroyed an Inquisition force guarding a Chaos artifact of great power and claimed it for their own.
After this and other conflicts with the Inquisition during the 13th Black Crusade resulted in them being declared Excommunicate Traitoris and were all but destroyed by the Grey Knights. Only a few hundred survived and its believed they fled to the eye of terror.
Some of this is covered in the novel Angron's Monolith
The space wolves are known to claim spacecraft they board for the chapter if they can be cleansed. This has allowed them to amass and maintain an abnormally large fleet for Space Marine standards, consisting of 8 Battle Barges and many other ships. Codex: Space Wolves (7th Edition)
Logan Grimnar uses the axe Morkai. The axe is from a Chaos Champion of Khorne Logan defeated in battle on Armageddon. Before he would use it he had it reforged.