Borderlands 2: What Marcus says if you don't steal from him (spoilers).

In the mission "Where Angels fear to Tread", after Lilith teleports you back to Sanctuary, you'll end up in the backroom of Marcus' shop.
There are quite a few chests you can loot. If you do, Marcus will yell at you, saying you robbed him blind and iirc, will also be upset for your tresspassing.
However, if you don't take anything, he'll only get upset and with and mention the trespassing.
A neat little detail they thought of :).
Note that I'm using the BL2 Reborn mod, which may have added this in.

[@MisterJohnDoe]

For some reason I've never once thought about this.

[@connorhamilton5707]

I'm glad somebody checked this as I recently got the game and was curious in TVHM. Wish he would be a little more grateful though.

[@PumpkinCake]

I was curious about this on my TVHM playthrough, but my teammate started looting before I could say "Hey, wait"