Let's say you had a small automotive museum you would only show to friends who came to visit. In your garage is a small assortment of cars and then in the next room is your collection of automobilia. What engines would you put on pedestals for others to awe? Cost is not an option but space consideration is as you have room for only two or three engines to display.
Here are my favorites which strike me as being handbuilt art:
Renault Gordini V6 Turbo:
Any Lamborghini V12 with carbs:
Any Cosworth DF-series V8:
What about you?