@bel422 @yim Welcome!
@marrt great list! Like you, I have a couple of implements that didn't pan out (fertilizer spreader for us, as I used it once (worked great), and decided to change our land use practices), and some that really did, e.g. forks, the LMB, post driver, trencher, and rototiller
I am more of the cost/benefit mindset, and I think it depends on individual needs and uses.
When we bought this property, I could see that it had a number of projects that were in need of either repair or building. Of course, a bunch more emerged after the fact. After a broken main water line (I do not recommend excavating fully saturated wet clay soil by hand, misery) that the 4n1 bucket made pretty quick work of, and a large drainage project that was a hoof saver for the horses, and to me, mentally, the tractor paid for itself very quickly. Had we outsourced a number of those projects, several would have been close to the purchase price of the tractor, redoing the wood fencing more. Overall, I know we are way ahead, but I didn't buy it just to mow, or rototill, or any one thing, I bought it as a force multiplier to enable me to do more projects, more quickly, and at a lower cost to me.
All the best,
Peter