Too many to list - these are just a few...
Cradle cirque under Cradle Mountain, Tasmania. I walked the Overland Track a number of times when I was young and my strongest memory is of the autumn fagus leaves (our only deciduous native I think) on the cirque.
Just about anywhere in Kyoto, Japan. You don't need to go to all the temples and shrines to get the wonderful character and sophistication of Kyoto. Osaka is crass and commercial in comparison and Tokyo is just too big.
Shirakawa - go Japan. World heritage village with the most amazing big thatch roofed farm houses...and fireflies. Actually, I'm pretty happy in just about any mountain village in Japan - especially if there's trout sashimi and mountain vegetables on the menu.
Sydney Harbour - lots of memories from my student days of picnics and sailing on the harbour.... 'as the Manly Ferry cuts its way to Circular Quay'. I wish I got back more often.
Central Thailand - Sukothai, Pitsanulok, Mae Sot... I have wonderful memories of this area when I was a young backpacker. The night markets had the most wonderful coconut cake - and 20+ years later I've just got a recipe from a Thai blogger which I'm going to try this week.
Florence and Assisi. I love the colours of Italy and have especially happy memories of both these places...
The view from the Empire State Building - pure city. I didn't expect to be as impressed as I was.
My garden. With a family, a business and a mortgage I don't travel very often very more but when I have a day off I'm very, very content to potter in my garden. I think I'm starting to get old.