There aren't too many examples of dangerous game in the UK - shooters will usually pay lots of money to go on hunting holidays in Africa or Canada and the USA to try their hand at taking down some big game. You'll need a pretty powerful shot to take down animals like Buffalo, Bears, Mountain Lions or Wild Boar, so a bolt action rifle is the primary choice here. Something in a bigger calibre like a 700 Nitro or a .50 will do the job, but you'll have to be careful - this is dangerous game after all!