Rollerball Pens
Rollerball pens are similar to ballpoint pens in that they both operate by a tiny ball distributing ink onto the paper, but the ink in a rollerball pen is water based, like you would get in a fountain pen. This means that a rollerball pen needs a cap, to stop the ink from drying out, and also it means that the writing style is much more fluid than a ballpoint, while being much easier to maintain than a fountain pen.
Rollerball pens are a half way compromise between the two, taking the ease of use of a ballpoint, and combining it with the elegant writing style of a fountain pen.
Pilot
Pilot V Sign Pen
Faber-Castell
Faber-Castell Fast Gel Pen
Caran d'Ache
Caran d'Ache 849 Rollerball Refill
Faber-Castell
Faber-Castell Free Ink Rollerball Pen
Schneider
Schneider Topball 845 Rollerball Pen
Uni-Ball
Uni-Ball UM-120NM Signo Gel Ink Rollerball Pens - Decorative Colours (Pack of 3)
Multipack of Uni-Ball UM-120NM Signo Metallic Gel Ink Rollerball Pen