In no particular order: Poland, Russia, Iceland, at least one Scandinavian country (you're all so amazing I can't decide on just one

), Ireland. I'd like to chuck Switzerland in too, but I'm not sure who it'd bump off the list

.
Poland 'cause a recent chunk of the family tree was from there, and it would be interesting as a place that not only geographically, but also culturally in between Western and Eastern Europe.
Russia would be stunning to see from one side to the other, due to the sheer quantity of land and peoples it encompasses

.
Iceland looks cool and sounds like it would provide lots of opportunities for adventurous adventures.
Scandinavians seem to have a lot of things worked out a lot better than most other places, and I'd like to visit and see what their countries are like. There's also plenty to see and do in each nation, but I figured I'd give a less common reason to go there

.
Ireland is at the end of my eloquence -not that there was any to start with- so I'm having trouble articulating the reasons. But it caught my eye many years ago, so I'll try to drop by if I get a chance.
EDIT: Perhaps I should mention that I live in/grew up in Australia, to give a little more of and idea of where I'm coming from.