Pens available in 1.0mm thickness. These are often referred to as "Bold" pens, as they put much more ink on the page than thinner, say 0.7mm or 0.5mm, pens. This means excellent smoothness when you are writing, but often it can lead to ink bleeding through the page and added smearing if the ink doesn't dry very quickly.
Are you looking for the best 1.0mm pen? We'll save you some time... The best 1.0mm pen is the Jetstream 101.