You bet your life!

You bet your (sweet) life!

 and You bet your boots!; You bet your life!; You bet your (sweet) bippy.
Inf. Fig. You can be absolutely certain of something! Mary: Will I need a coat today? Bill: You bet your sweet life! It's colder than an iceberg out there. Bill: Will you be at the game Saturday? Tom: You bet your boots!
See also: bet