NirSoft provides a unique collection of sysinternals like small and useful freeware utilities. Most of the NirSoft utilities which overlap with Sysinternals tools aren't good as Sysinternals, but the rest of the utilities are valuable addition for anyone who wan't to know what's going on in his computer.
To list some of utilities what I find useful...
OpenedFilesView - displays the list of all opened files on your system.
RegScanner - find the desired Registry values that match to the specified search criteria (good one)
ShellExView - displays the details of shell extensions installed on your computer, and allows you to easily disable and
enable each shell extension.
WinUpdatesList - displays the list of all Windows updates (Service Packs and Hotfixes) installed on your local computer.
SmartSniff - allows you to capture TCP/IP packets that pass through your network adapter, and view the captured data
CurrPorts - displays the list of all currently opened TCP/IP and UDP ports on your local computer.
(overlaps with sysinternals Tcpview, but I prefer this one)
Hello !
KR