Eddystone (change the front sight blade to thinner blade)
I went the other way, I put a thicker front sight on my M1917 Eddystone.
For a "unique sight" don't forget the Model 1901 Sight for the Krag rifle, It has three notches and a peep, The first notch was for BSZ, set for 375 yards, had a "B" marked on the left side of the sight base to indicate BSZ. The U notch on the slide went from 450 to 1900 yards. The peep went from 100 to 1775 yards, and the top notch was for 2000 yard shooting.
It also had windage adjustments by pivitoing the sight, there were marks for this but were set for 5.86 change (IPHY) at 100, Rather course for precision fire.
Also the 1903a3 sights were good, but you were limited to 800 yards with 100 yard increments and the windage adjustments were course, 4 MOA.
That brings us to the M1/M14, in my opinion the best sights on a battle rifle, positive 1 MOA clicks from 0 to 1200 yards and positive 1 min windage.
The M16A2 were close, better yet on my civilian version, (White Oak) which is .5 Min Clicks. You don't have the range using the rear sight only but no biggy if you use your front sight.
For example on my White Oak to shoot 1000, I simple use my 600 yard zero and screw down the front sight 4 full revolutions.
Still, my personal opinion, the M1/M14 were the best military sights made if we're talking sights only. (Not that there is anything wrong with either rifle, both are great, just heavy for humping days at a time.