Some tools which I really find helpful are:
a. Multimon – Support for multiple monitors
b. Process Monitor
c. Process Explorer
d. Desktops – Desktops allows you to organize your applications on up to four virtual desktops.
e. OleView – For COM purposes
f. Spy++ – For windows GUI handling
g. Resource hunter – Reading resource files. It will be helpful when your working on multiple languages.