Tools are decided by Management i.e., the company you work 
for. since some tools require budge. Some tools can be 
downloaded from online and free to use.

Depends on the Project - if the project has any future 
releases - a test management tool is necessary and for the 
regression purposes, an automated tool is necessary to 
execute regression scripts.
If the project is used by a large number of users, to know 
the performance of the designed application a performance 
test tool is necessary.

Excuse If I am wrong
kiranmayi
bommi_ki@yahoo.ca