Brag about shit you've made in or for videogames. Maps, sounds, models, skins, etc. etc.
I used to do a lot of mapping for Half-Life 1... and when I say "a lot" I mean "a lot" -- all the 3D artwork in my gallery is me abusing Hammer and Half-Life and using them as a subpar 3D art program. Most of it was never released or even shown to other people though.
My last release was a map named DM_Enpro, a cramped and gloomy map set in a futuristic atmospheric processing plant, with lots of dark and claustrophobic maintenance crawlspaces. I recently reopened the old RMF (editable map filetype) and was mucking about, and I was surprised by the amount of work and attention to detail I'd put into it. Every intersection or interesting doodad in the crawlspaces was labeled with a unique sign that was largely meaningless but still had an air of purpose to it ("JUNCTION 7-21R", "ACCESS 7-16A", "SVCPANEL 7-75L") and I'd modified a couple stock sprites to make steam jets or water dripping from pipes.
Two scrolling text billboards had announcements for the area's fictional employees and referenced things in the map, while the mess hall had a full and readable menu. Through the mess hall windows could be seen a raging thunderstorm pouring torrential rain over a much larger, inaccessible part of the facility, all of it cramped and built onto itself to give the impression that it was not only massive but had been there for a long time; all the signs and hazard stripes had noticeable aging and wear on them, too.
I was never very good at drawing my own textures from scratch, so I most often just hacked together existing textures other people had made -- thankfully the vast majority of the community were pretty open and eager to share their textures.