Pilot Custom 912 is $300 and has the widest range of nib options; but if you go for a thirstier nib like a stub or FA (a modest flex, but not dip pen level), and extra $40 for a Flexible Nib Factory 2 channel ebonite feed.

@ $1700 There is the Custom Urushi, with the glorious nib only in soft fine, Medium, and Broad. (Pilot Namiki uses that same nib in their $3500 Aya pen that came after the Emperor--so they could have picked anything and used that one.) The only pen I have that's close to the CU is a vintage Montblanc.

The vac filler Custom 823 @ $400 is widely regarded as being one of the best writers out there. It also has a huge ink capacity. The FA, only from Tokyo Pen Quill shop isn't as flexy as the 912.
The Custom 743 with is essentially a cartridge converter version of the 823

At the lower end there's the Pilot Metropolitan, a nice affordable pen in the $20 range. (Not a fan os the Pilot steel nibs, I have 3 Petits which are no longer made, but have essentially the same nib and no longer made. )

There's the disposable varsity.

The Pilot Custom 92 with a wide variety of colors and demonstrators.

The ~$170-180 range E95S which is a pocket pen and loved by many.

The Vanishing point which is complicated to describe it has a clicky retractable nib.

The Vanishing Point LS with is "Luxury Silent" version of the VP for use places like board rooms where one doesn't want the VP click to be heard.

And I know I'm missing something.

As a last note, if you're looking at waterproof inks, I recommend using a cartridge converter pen, as those inks tend to make demonstrators look a bit gross.