cond2.js

function cond2() {
    var cs = [].slice.call(arguments, 0, arguments.length - 1);
    var ow = arguments[arguments.length - 1];
    return function() {
        var i = -1;
        while(++i < cs.length) {
            var value = cs[i].apply(this, arguments);
            if (value) {
                return value;
            }
        }
        return ow.apply(this, arguments);
     };
}

function ifTrue(pred, onSat) {
    return function() {
        return pred.apply(this, arguments) ? onSat.apply(this, arguments) : void 0;
    };
}

// example:
grade = cond2(
    ifTrue(R.gte(__, 90), R.always('A')),
    ifTrue(R.gte(__, 80), R.always('B')),
    ifTrue(R.gte(__, 70), R.always('C')),
    ifTrue(R.gte(__, 60), R.always('D')),
    R.always('F')
);

grade(55) // => 'F'
grade(66) // => 'D'
grade(75) // => 'C'
grade(80) // => 'B'
grade(99) // => 'A'

Not sure those are really needed, but it may be more extensible in the future compared to array tuples.
Otherwise i don't see why tuples wouln't work as well