Something scientific and/or military that will be a keepsake: the most expensive
telescope you can afford.
Reasoning: a lot of scientific stuff goes cheap after a while, or out of fashion, or is replaced by a newer technology. But the universe will never go away, we hope, and quality optics seem to always be expensive through the years.
If you are looking to spend even more... something scientific and/or military that will be a keepsake, for somebody unemployed right now: his first pilot logbook, and a few lessons at the local flight school.