For me recently it was a couple of gigantic box cushions for a large garden seat in between 2 big raised beds built by son in law.
Having rashly promised to make some, since nothing to buy would fit and would be so expensive to have made, I then wondered whether I was mad! (Or rather more mad than usual...).
However, I ordered 2 big pieces of foam to fit, and then fiddled out patterns, with the help of squared pattern paper from John Lewis.
Lovely garden-flower fabric also came from JL.
My only sticking point was zips long enough to go right round the ends so covers could come off for washing. I was too dense to think of what Dh finally suggested - 2 to meet in the middle! Dhurr... I do sometimes wonder where on earth I was when logical thinking was being dished out!
But they turned out so well and have been much admired. When not used outside they live in dd's new kitchen extension, where little Gdcs enjoy jumping/playing on them.
I'm sure other GNers will have rather more accomplished projects under their belts, but that's my best so far.
20mph speed limit....for or against?
How to be happy - 5 golden rules