OllyDbg (V2.1) – This tool is mostly for examining malware and programs. I find the tool really useful, the Assembly is very good too, especially with tracing JMPs.
Download – OllyDbg 2.0
Hook Analyser (2.6) – Able to view application crashes with more detail, and hook onto running processes for malware analysis and debugging.
Download – Hook Analyser Blog
WinCheck (8.50) – Able to view Kernel Data Structures not available in WinDbg.