I picked these up this morning while out. There were absolutely loads of these tiny pods on the ground and I drew the line at getting on my hands and knees on the pavement to take a photo (too much passing traffic and spectactors!) I think they're either baby sweet chestnuts or baby horse chestnuts. Either way they looked quite pretty and green for today's picture.
I like the interesting spiky pods. I would have picked them up just so I didn't have to get down on my knees. I do that only as a last resort (aka - very rarely).