there r different types of tools r there in teh market for test automation
for functional and window based applications: winrunner
Java Based applications : silk
To Test Load And Performance of the web applications:LoadRunner
To test .net,java,sap,people soft,siebel,et.c :QTP
so depending on the crieteria we can decide which tool we have to use
suppose if u want to test web application functionality u can use either winrunner or qtp qtp is is advanced one having extra features
if u want to test the performance u can use Load runner
purely java besed application we can use silk