Edge Retention

Of all the knives you've had/tried, which one has the best edge retention? please state, type of knife, steel, maker, and if you're in a pro or home kitchen set-up…

I have a nakiri and a 240 gyuto in HAP40 by Shimatani. Home environment. I use the nakiri several times a week and haven't sharpened it since before Thanksgiving 2013. Getting to where I need to sharpen it but you get my point. I'm the third owner of the gyuto and I don't believe any owners have sharpened it yet.

What is the definition of "sharp" for you ?? If a knife doesn't respond to stropping or the edge feels fatigued or doesn't scare me anymore I know it needs sharpening. It can be a week , day , month depending on the knife also depending what do you mean by sharp . Some chefs I have worked haven't put their knives to stones for years and they are perfectly happy with blisters on their hands from pushing knife down whatever they are cutting .
Best edge retention I had was from miyabi mc7000( zdp-189) I wish they had an ok handle at least

SRS15 and R2 knives take a great edge and hold them well

Great points Mert. Also consider how gracefully the steel degrades. Some high vanadium steels have the reputation of quickly losing the scary edge but maintaining a 'serviceable' edge for a long time. In my experience HAP40 stayed scary for a long time and then just fell off a cliff.

Home cook here
CMP154 k-tip 240mm gyuto by butch harner
followed by SB1 (niolox) guyto by Schanz and custom niobion steel by Koraat.

These three maintained a good sharpness (armhair shaving) for a really long time!