I've used a the Logitech MX518 for more than a decade. Went through a few of them, the design just fit my palm perfect, I dread having to use anything else, specially those shitty razer designs, eww. The Deathadder is one of the worst mouse I've ever held. The MX518 and similar designs, are designed for the palm grip where you rest your entire hand on the mouse, most FPS players for one reason or another use a claw grip, except me, I like to rest my palm and the bulgy of the MX518/G400s design helps filling it up, it also helps avoid Carpal tunnel syndrome, which I fortunately never suffered from.
Anyway, for a while there these were discontinued, so I had to get it's successor the G400S, which is exactly the same shape.
The MX518 was rereleased in 2019, so it's back on the market, I might get it again if my G400s breaks (been going strong since 2013, these things are really well made)