All reasonably stable tools
AccessMask - decode access mask for common object types
BgInfo - WPF version of the Sysinternals BgInfo tool
CpuStres - thread/CPU stress testing app
DebugPrint - monitor OutputDebugString/DbgPrint(Ex) calls (no driver needed)
DriverMon - monitor any driver activity
ErrorLookup - error code description for Win32 (GetLastError) and NTSTATUS
ETW Explorer - view ETW XML manifests for registered providers
GFlagsX - enhanced version of the GFlags tool
Kdump - generate a local kernel dump
Kdump64 - generate a local kernel dump (64 bit)
MetroManager - list (and launch) installed Windows Runtime components and apps
MemMapView - view any process memory (including protected and minimal processes)
NtfsStreams - show NTFS alternate streams in files
ObjDir - command line tool to show object manager namespace
QSlice - modern version of the classic QSlice tool
QSliceX - pie chart graphics for QSlice
PEExplorer - PE file viewer
PoolMonX - kernel pool memory allocations
PdbView - view PDB files
PerfMonX - enhanced Performance Monitor tool
ProcMonX - ProcMon-like tool based on Event Tracing for Windows (ETW)
Sysrun - run any executable with the SYSTEM account (no service needed)
System Explorer (SysExp) - system, process, thread and other information - all in one tool (WIP)
WindowTitleEx - Show HWND, TID, PID on windows. Revert with included tray icon
winsta - Show current session's window stations, desktops and top level visible windows (with non-empty titles)
XCalculator (XCalc) - simple calculator supporting variables and functions