Today's What's This? is one of those plants that you'd overlook easily. I think it's a weed to be honest and the photo below shows it growing in a drain; this example is quite bushy but other examples I've seen are leggy with no real form. Close up, it has small, pink flowers which grow in spikes. The flower buds seem to be enclosed in bracts with colourful green veins which remind me of Golden Candles or justicia.
STOP PRESS! After typing that I was reminded of justicia, I went searching and I think this mystery is solved.
I found photos of justicia betonica or white shrimp plant. Would you agree? It's listed as a herb on some sites, not a weed.