My personal favorite is how Boles drinks from his flask once or twice in the beginning of Arkham Asylum.
Clayface Joker not having a skeleton when you look at him in Detective Vision.
The buildings in Arkham night were nice. Lex Corp. Arrow and a few more.
The way Nightwing interacts with Penguin in GCPD Lockdown! I never knew Dick and Penguin would or even could have that much chemistry and it’s something I would love to see more of.