The speed of light seems to be the undisputed speed limit of the universe, in relation to the fact that to travel faster than a massless photon is able to travel would not only be physically impossible because no object containing mass would be able to stand the blinding speed, even in the vacuum of space without atmosphere to create drag.
Also, there is the time aspect. If you are on a spaceship going 99% the speed of light, and your twin brother is on another spaceship going 9% the speed of light, traveling to the same location, by the time your twin were to arrive, he would have experienced 90% more time than you have, even though you have both travelled the same distance.
Also, traversing the universe at the speed of light, for a human, would require technologies that we could only dream of.
First, you would need to somehow find a way to shield the inhabitants of the ship from the deadly effect of inertia and g-forces inside of the ship. For a human, 186,000 miles/second would kill in a fraction of a millisecond, the force would flatten all of your internal organs, your brain, your eyes, everything, against the back of your body. Bones would literally liquify, the heart wouldn't be able to beat against the immense force of inertia.