>  * at most THREE proposals per person
>
>  * submission deadline: 6/30 (Sat) 23:59 UTC

Dang and I just saw the invitation message and deadline.
Well, anyway if I were to submit proposals, they would be for

Object#present? (like rails')
More #blank? methods to mirror #empty?
Object#try (though apparently with some other name Matz likes).
More #contain? methods

Too bad I missed the deadline oh well.
Cheers!
-roger-