Another language feature I want:

An 'in' keyword.

if (x in (1, 2, 4))

Seems pretty simple, and it'd be a boon for clarity, especially in cases like:

if (x == MyEnum.MyValue || x == MyEnum.MyOtherValue || x == MyEnum.MyOtherOtherValue)

Scoping the list would be interesting too:

if (x in MyEnum.(MyValue, MyOtherValue, MyOtherOtherValue))

is much easier to follow than the alternative.