Common:
* Loo: This is the most common slang term and is widely understood.
* Toilet: While technically the proper word, it's also used colloquially.
Less Common:
* Bog: This is a bit more old-fashioned but still widely understood.
* Lavatory: This is more formal and usually used in public settings.
* The Throne: This is a humorous term, often used jokingly.
* The John: This is an American slang term that's sometimes used in the UK.
Regional:
* There are many regional variations, like "dunny" in some parts of the UK.
It's worth noting that the use of these terms can vary depending on age, social group, and region.