In the UK, virtually every room comes with small packages of biscuits set with the tea pot/cup and tea bags. I consider the biscuits and tea bags to be consumables and have no issue taking a package of biscuits that I didn't eat during my stay. The tea pot and cups are a hard no.

As others have stated, I subscribe to the general rule that consumables are fair for the taking, but items that are furnished as part of the room are not. Take the newspaper left at the door, but not the hardbound copy of "Things to see and do during your visit to XXX". Pens and notepads are okay but not the leather folio that holds the notepad. Mini shampoo bottles are okay (although I have a couple from Thistle Hotels that I've been refilling at home for 15+ years).

As for mini bars, I've often encountered rooms that provided complimentary bottled water and maybe a couple of KitKat bars. I consider these for my consumption, and if I don't use them overnight, I'll grab them to eat/drink on the way to the train/airport/etc.