Great thread this.
When i can, Im always garden watching, you just never know what might turn up.
I suppose the best butterfly seen in my garden are WLHs. I first spotted them several years ago, climbed on my shed roof, and took long distance pics of them leaning into the elm leaves. At that time, i didnt know what species they were

because i had only just started observing butterflies!
2 years have passed since i last really saw them, but this year(being what it is) has seen them once again return.
I should check my overal garden list too, because this year i added 7 new species/types.
I live in a suburban area, but my garden does back onto a wooden area. I aslo have an overhanging oak tree(next to the 2 elm trees) so this year i was leaning out my bedroom window, to photograph a PH!!
This WLH flew onto my lawn(i was looking out the window at the time) so i shouted to my wife to
keep an eye on that butterfly I grabbed my camera, ran downstairs, and took several photos.
This photo was shot on the 14/7/13, i had seen them the previous day too, and judging by the wing damage, they had been out on the wing for awhile.
3 years ago, I spotted them flying around in my garden, in the last week of May!
Cheers Paul.