What are some alternatives?
When comparing Gucharmap and Extra Keys, you can also consider the following products
WinCompose - WinCompose supports the standard Compose file format.
Event Viewer - Get help, support, and tutorials for Windows products—Windows 10, Windows 8.1, Windows 7, and Windows 10 Mobile.
Holdkey - Holdkey is a Windows program that makes it easy to type characters with accents.
PopChar - The character map that works!
BabelMap - Unicode Character Map for Windows
SymbSearch - A tool for searching unicode-symbols and copying it to the clipboard.