There is a part of me that thinks that buying a fake - from someone selling them as reproductions - for space fillers for something like, say the 1798 Dorrien Magers shilling that only 20 still exist - is fine. Pay $5 since I'll never probably even see a real one and concentrate on spending good money for the real ones like the 1787 I got recently.
But no sympathy for anyone trying to pass a fake as real.
My favourite coin in my collection would be the Gothic Crown, but I have posted that many times before.
Second favourite is much more difficult as there are many candidates, but this one is high on the list - 1723 SSC Crown. You see the shillings all the time, but the Crowns are much scarcer.