my best wierd gun is a limited run conversion of deact AKM into Brocock air cart rifle.
Mine was the only one made in .22 from approx 10 or so done.must make it a bit rare as you definitely cant buy them now

.....or the conversion of a 1942 no4mk1 lee enfield by S&P who did about 200 but there will be very few of those left now..shame