Neptune's rotational axis is reasonably near-horizonal: that is, it lies much closer to the plane of the planet's orbit than is the case with any other planet of our system.

Also, it uniquely rotates "in the wrong direction", when compared with the other planets.

A distinction as to Sirius -- it is the brightest star in our sky (apart from the very occasional supernova), but not the most luminous. That is, others cast off more light, but Sirius appears brightest to us because it is far closer to us than those more-luminous stars (and is far more luminous than the closer stars). In technical terms, it has the greatest magnitude but not the greatest absolute magnitude.