Hi Atul,
Below are a good number of threads on the certification help.You can give certification without attending training, provided you are confident of your skills to clear it.
http://scn.sap.com/thread/3384690
http://scn.sap.com/thread/3379611
http://scn.sap.com/thread/3349670
http://scn.sap.com/thread/3231606
http://scn.sap.com/thread/3286588
Thanks
Mallik