In the DOS era, we generally used the PCTOOLS5.0 to edit file code, but since the FAT32 file system came out, PCTOOLS5.0 was unusable. Seldom excellent file code editor appeared until this WinHex from Germany, which can be regarded as the best hexadecimal editor for file, disk & RAM after the former.
IDM Computer Solution's UltraEdit claims to be the #1 and simply the world's best text editor in the world. Actually this's relative, just as a lot of reviews for some great software you can see in AppNee - most of which depend on personal use experience and habits. Anyhow, we can't deny that UltraEdit is really powerful.
Hex Editor Neo is a professional and powerful binary, hexadecimal file viewing, editing & creating utility for both 32-bit and 64-bit Windows. It came with abundant and convenient features, and was specially designed for software and hardware developers who often deal with ASCII, hex, decimal, float, double and binary data.
Modifying the data in memory can be not only used to decode/hack software, also used to hack all kinds of games (especially PC games and emulator based video games). Cheat Engine (CE for short) can make one game easier or more difficult, in other words, that's to be more suitable for you (but not necessarily to be more interesting)! Its principle is - the memory debugging/hacking.