This is question that has stumped many an interviwee.It is 
asked to ascertain how much you know about your self.A 
person who knows oneself well is likely to be more 
effective in life.However, many interviewee find it 
difficult to verbalize their strengths and 
weaknesses.Interviewee try to give weakness that will not 
jeopardize their chances in disarming ,sincere and 
honest.Remember to go to your next interview having thought 
out well in advance what your strength and weaknesses are

sorry ,continuation for the above answer here
you can say,your strengths as 
Test to break attitude
Motivation towards quality
Continuous process improvement
Good test case developement and testscript execution skills

Its very good Questtion and its very simple , with delay 
and any hegitation say  Strong in Regression Testing Thats 
all . Any tester must do  regression and its depeding on ur 
skill too
All The Best

thanks guys.Thanks a lot satya.

u r answer is exactly right satya. One more point is every 
tester thinks always negative sense in that situation