Not ever having shot a tiger, and really not desiring to, I bet when facing one up close and personal nothing you hold in your hands would feel big enough. But, like Joe said, it's all about bullet placement and keeping a cool head when facing a creature that would cheerfully eat you.
I suggest that a 70 grain .22HP bullet placed anywhere in the central nervous system from the head back to the spine would be instant lights out. Execute a heart/lung shot with the same bullet and Ol' Tigger would have plenty of time to shred your sorry butt before he expired.
