Crysis Hi-res icon (Maximum Res)

The icon embedded in the executable for Anodyne 2: Return to Dust has blurry interpolation between pixels, despite having an original resolution of 16x16. This even affects the 16x16 version of the icon, so it likely is some weird quirk of Unity. I have manually recreated the icon pixel-by-pixel and integer upscaled to all major icon resolutions except 24x24 as to achieve a pixel-perfect upscale.

Need for Speed: Most Wanted - HiDPI icon
By TripleZet https://www.deviantart.com/triplezet
Source: https://www.deviantart.com/triplezet/art/Need-for-Speed-Most-Wanted-HiDPI-icon-745415159 
Original icon for NFS: Most Wanted reworked in high resolution to look as close as possible to original 32x32 one.
If you need something bigger than 256x256, feel free to use 640x640 PNG preview (from Source)

The default icon included in the executable of Forsaken Remastered is only included in the size 256x256. Due to this, Windows uses nearest neighbor downscaling to create the 16x16, 32x32, and 48x48 icons when they are needed (such as on the taskbar or in the Start Menu). The icon file provided here includes these resolutions and more, linearly downscaled from 256x256 to preserve clarity. It also includes the 8-bit 32x32 icon from the original 1998 release of Forsaken.

Or the curse of GOG not using the original icon for games, take your pick. 
The GOG version of The Curse of Monkey Island does not include the original executable, and as such the original icon is missing (due to GOG always using a different icon from the original). Additionally, the Steam version uses a lower resolution than the original (32x32 instead of 48x48). The icon provided here is taken from the retail executable and upscaled to scale nicely on Windows Vista and newer (as well as Linux).

Higher quality icon for Black Moon Chronicles, taken from the splash screen of the editor and upscaled twice with waifu2x.
Comparison: https://community.pcgamingwiki.com/gallery/album/142-black-moon-chronicles-icon-comparison/