What sprite sheet ripping program is easiest and best to use?

[ZeldaClassicEXPERT]

I am talking about perfectly [like one pixel left right up down etc. of the sprites height width etc. or exact amount of pixel height and width for each sprite etc.] ripping sprites
what product(s) that are safe to download can I use
to easiestly and quickly rip sprites from sprite sheets please? Thank you.