Iambic keying with a dual-lever paddle is by far the most popular form for Morse keying. But in recent years an old alternative has reemerged. This is the Ultimatic mode which goes back to
W6SRY in the 1950's.
The experience seems to be that it needs less timing precision than the iambic mode for letters like A, N, R, and K (· —, — ·, · — ·, — · —). When both paddles are squeezed, the last one to be pressed takes control. So when right-left is pressed one gets a dah followed by dits, not the dah-di-dah-dit of the iambic keyer.
It is very simple to add code for an ultimatic keyer to an iambic one. In recent years this has led to an ultimatic option in some stand-alone keyers, such as: