To be as sharp as grandpa used to keep his knives― very, very sharp. Sharp enough to shave with or cut through paper easily. Much sharper than dad-sharp.
As sharp as your dad used to keep his knives― sharp but kind of dull, for safety. Not as sharp as grandpa-sharp.
With this you could cut a medium-soft cheese with some effort!
A type of gamer (esp. in CS:GO) that is very concerned with buying pretty, expensive weapon skins and knives rather than having successful or fulfilling gameplay.