Favorite Game Boy game? (Game Boy, Game Boy Color, Game Boy Advance)

This can be any game for any of the handhelds or even device like the Game Boy Camera/Printer or the e-Reader.  One game I love for the Game Boy Color is called, "Pocket Billiards: Funk The 9-Ball" and it's really fun!  It's a billiards game, anyone who's played pool knows how it works.  But this version of the game adds something extra to it.  Every colored ball has a different power up effect.  That can either help you or hurt you as you take turns with a friend while playing or really screw you over when playing against the computer.  There are different characters in the game too.  The art style is that superflat art style from the late 90s to early 2000s that used to be all over Japanese games at the time.  Those thick black outlines, that cartoonish style mixed with anime with the big heads and big eyes, the bright colors, ect.  It was only released in Japan back then but has been fan translated.