Sometime around 2010 I discovered the Bic Atlantis pen, and have been using them exclusively since. I purchased my first pack of the new Bic Glide (supposedly nothing changed with them other than the name).
I have liked this pen because not only do I get little to no smudging, but I do not get the choppiness that i do with some other ballpoint pens.
I used to use a lot of felt tipped pens in my youth, but in 2003 I started to work for a research laboratory and there are quite strict rules about which pen you can and cannot use. Felt tip pens were out.
All about the Pilot G2 0.5. They've got a smaller size that I tried but the ink didn't come out consistently enough so I had to go back to the bigger one
Personally I like the Tombow Mono Graph 0.5 and mono-wx 0.5mm HB leads. Switching to HB leads from 2B leads has been the best stationery related decision I've ever made, and I recommend every leftie to experiment with harder leads. No more smudging the paper with graphite because of your hand running over the paper. I will probably try the 0.3mm version of the same pen the next time I go to the stationery store because I want to experiment with finer lead thicknesses.
The Zebra Sarasa X20 Dry has been my go to for a long attempt at finding a small diameter gel pen. The whole Sarasa line up is pretty neat though. I think mileage may vary depending on indivudal writing techniques.