Store multiple things on Clipboard: Win + V
Various Windows keyboard shortcuts: Win+#, Win+R, Win+Shift+S, Win+E
Annotate and edit several screenshots at once: ShareX
“Better search” with Regex
Rainbow CSV plugin to view .csv, .tsv, any character-separated list
Fast PDF viewer: SumatraPDF
3GPP decoder (made obsolete by KS Notepad++ plugin)
uBlock Origin: element zapper