The Mithril Skateboard is a skateboard Scott wins after "defeating" Ramona's second evil ex, Lucas Lee, in Volume 2. The board is apparently stronger than many others and has the following stats: +4 Speed, +3 Kick, +1 Will. Despite its good stats, Scott is unable to use it since he opted out of the Skateboard Proficiency back in Grade 5 (in place of Longsword Proficiency, as we learn later). The board floats in midair for a moment before vanishing since Scott can't take it. Scott is unsurprisingly very disappointed, but Wallace tells him to suck it up.
Mithril (also known as Mythril and Mithral) is a rare non-existing element often mined and smithed into high-leveled and powerful weapons and armour in most Role Playing Games, including World of Warcraft and the Final Fantasy series. The concept of Mithril was first coined in JRR Tolkien's The Hobbit when Bilbo Baggins is given a Mithril vest by the Dwarven King which is impervious to all cuts and piercing. This item was passed on to Frodo Baggins in Lord of the Rings: The Fellowship of the Ring.