I agree asparagus peas look pretty but not worth growing. Had some success with sweet potatoes both last year and this but not a huge yield given the greenhouse space they took. Crystal cucumbers were nice, and cape gooseberries.
Grow quite a range of heritage tomatoes and much prefer the big beefsteaks. Stevia/sweet leaf yes still grow and use to replace some of the sugar in pies etc.
I have grown purple french beans, they're easier to find and pick but no taste diff. Yin yang beans I still grow, good dual purpose french bean/haricot. Grew a yellow wax bean but good runner beans take some beating.
When I first grew barlotti beans they got lots of oos and ahs but they're run of the mill nowadays. Tomatillos huge crop but regular toms just as good - I think most of the ended up in chutney.
Grew chickpeas last year for the first time. Once again, not worth the space they took up.
Good King Henry I've grown for ever, tasty early shoots. Grown several crossed berries over the years.
We had a medlar at our old house, very pretty spring flowers -made jelly from fruit. Grew it as not commonly seen. Gave up on Goji Berries last year after fussing over them for several years and no return. Started growing a mulberry til I realized how big it would grow so I passed it on to a friend starting a big orchard.
In the end we rely on the old tried and tested stalwarts.
I'm interested in your Daubenton Kale too.
Look at http://www.amishlandseeds.com/index.htm
for something different.