I'll start!
12 ballpoint pens from the pound shop - this week has been a joy, no scrabbling about trying to find a writing implement (and not having to resort to a stubby pencil or purple crayon)
An eye mask (£2.99) - nearly 13 years of trying to contort body and duvet to shield eyes from hallway light (needs to be left on for nighttime trips to the loo), it's transformed my nights!
£1.99 for proper glasses cleaner cloth, as opposed to t-shirt or tea towel - I can see again!
Any more for any more?