Nick Bounty said:
Ireland. There will be a lot of talk about a Gaelic rebellion here in the UK, but until some way of getting weapons from ethnic Gaels in America becomes obvious then it will be difficult to actually start one, despite the influence of fanatics. But in Ireland there are militant groups that will become a lot more powerful with the amount of effort in increasing the status of Irish culture. Legitimate nationalist claims are very easily hijacked when a civil war has really only just ended, and when the militant groups that fought it were not destroyed.
I strongly doubt Ireland, England, Scotland and Wales together could start a significant war. We just plain lack the forces and manpower for anything less than defense. By rebellion though, I assume you mean Civil War. In which case, England and Ireland have seen enough violence for now, let someone else have a go
Im gonna say Switzerland. Villainous dogs with mountains of Nukes and a grudge against every country in the world for ridiculing them.