Right now, unless you count it as part of my free "boring" spending, I'd spend it on repairing/replacing my (high end) office (gaming) computer. It's been down for weeks and... no work and no play makes me a human hand grenade. More than usual. Replace my laptop that broke at the same time.
But five grand, right now, nothing practical? Complete my Pathfinder and Starfinder collections, my Palladium collection, Earthdawn, Rokugan d20, start and finish my Sine Nomine set. Back ACKS II to the hilt.
Custom leather wheelchair accessories-- a white backpack and pink armrest bags, with brass fittings, large rugged compartments and padding. A lap blanket.
Clothing. Recently found a manufacturer of kilts in tartan colors I enjoy. More 80s-90s nostalgia novelty tees featuring the usual suspects: Mario etc, TMNT, He-Man etc, Marvel. A much nicer CC vest than the one I own, holster setups. Could use some more guns.
Take my daughter to the Melting Pot in Fort Collins. Take my whole family to Rodizios. Couple times, maybe.
Spend the rest of it at Steam and DTRPG.