I really dislike air fresheners.  I keep a bottle of mens UDY Paris cologne in the boys bathroom and that has a lovely smell. The downside is that if anyone wears Paris cologne they smell just like the boys room.

A few more awful smells. Fertiliser like blood and bone, fish sauce and shrimp paste.
Maybe I just dont do fishy. Whenever my OH has sardines, herring and/or kippers I seem to smell it everywhere. In the sink, the cloth, the tea towel and the bin!! Agghhh.

too many to list however the smell of someone dying would be the worst..I will never ever forget that one

The smell of a sweaty camel is not too pleasant.