I'll be damned

damned if one does and damned if one doesn't

Of a situation where either choice results in a negative outcome.

I'll be

Expressing surprise.

I'll be a monkey's uncle

Often preceded by well: expressing complete surprise or disbelief.

I'll be bound

An expression of surprise.

I'll be danged

An expression of surprise.

I'll say

Used to indicate emphatic agreement

I'll tell you

Synonym of I can tell you.