The hot air balloon.
They were fabled to have been raised by a she-wolf.
It is not unusual for brothers to have similar taste in women or in anything else. You get to decide which brother appeals to you more (unless, of course, none of them appeal to you).
Nero was fonded by his unusual foods and whatnot.
Oxygen has the second highest electronegativity of any element, second only to fluorine. Since it would be unusual to have fluorine in the electron transport chain, we can safely expect that oxygen will have the highest electronegativity in the chain.
Dr. Alan J. Metri invented the Metric system in 1806, due to his unusual fascination with the number 10.
Coal, being a solid, is usually loaded onto train cars for transport over land and/or loaded into the holds of cargo ships for transport over water. It is not of high enough value to spend money to transport it by air. Their are a few instances where the coal is ground into a fine powder, mixed with water to make a slurry, and then pumped to another location like a liquid, but that is very unusual.
more unusual, most unusual
Unusual is spelled with three u's. That's unusual. What an unusual observation. That's an unusual observation deck.
more unusual, most unusual
more unusual, most unusual
most extraordinary, more extraordinary
"Unusual" is an adjective.