I have used LN-BTC to purchase giftcards for some games I play and services I use. I've noticed you can even pay your phone bills or groceries by purchasing giftcards for those with your Bitcoins.
While I love online payments in that sense, how about a standard merchant accepting Bitcoin Lightning? I do recall Breez having a "Merchant Mode", but I don't know how practical it is, simply as I am not a merchant.
Is it just a concept that is yet to spring into (mainstream) action? I have heard about that one Burger place that accepts Bitcoin Lightning, but not much else in terms of retail mainstream acceptance of Bitcoin. I would love to see consumers be able to use their satoshis to refuel their car, shop for instant noodles at convenience stores, etc. Not have to pre-purchase (and then also use within the allocated time & not forget about it) a giftcard then walk to a store/order online.