Not a lot of point in jobbing backwards but on pure financial grounds I do regret selling my 3 Whiscombes. A JW65, a JW70 with .177 & .22 barrels and a JW80 FAC .22. In fairness I hated the JW80 but the other 2 were lovely guns.
As I've said my regrets are only financial-the most I got for any of them was £1200. In terms of 'shootabliity' none of them were particularly outstanding. My currently owned Park 93 shoots every bit as well as any of them AND it only needs a single cock. Why a JW should today be 8 to10 times as valuable totally eludes me. On the triple grounds of performance, quality of build and rarity the Park is every bit as good. The JW80 I actively disliked especially having to cock the rifle 3 times to get 27 ft lb was a real pain. The Theoben Eliminator is a better gun in every way.
On a more reasonable level I do regret selling a very nice Venom lazaglided Webley Longbow in .177 with a very neat walnut ambi stock and also a SFS Banshe in .177 (HW95 stage 3 tuned by SFS) although the Banshee went to a good friend who still uses and loves it many years later.