I was trying to imagine how it got here, alone on the wall with no berry producing shrub/tree above it. Possibly a bird dropped it, hence it looking a little squashed and exuding juice, as it flew over. Maybe a squirrel had amassed a little stash and was transporting it to their secret feast lair when this berry rolled off the top of their load.
It's definitely not a holly berry, it’s too pinky and juicy. And then I'm afraid my berry knowledge fades until the larger blackberry, strawberry and raspberry come into play. It'll just have to be a lone berry.