Common loanword for a cigarette, used in everyday contexts. Often interchangeable with タバコ, though タバコ can also refer to tobacco in general.
彼はシガレットに火をつけた。
He lit a cigarette.
シガレットの吸い殻を灰皿に捨ててください。
Please throw the cigarette butt into the ashtray.
cigarette paper
cigarette lighter (in a car)
Borrowed from English 'cigarette'.