Looking at my browser, they would see I keep a ridiculous number of tabs open, that I'm single and use dating websites, that I'm really into vintage bicycles, video games, and LGBT related stuff, and a few links to random porn videos.
For the rest of it, a bit of music, a few games, random funny pics and pics of bikes, and a bit of furry porn.
My desktop has most of my stuff on it, but it's got a fried motherboard. I now live alone, so I really don't care about hiding stuff on my laptop.
If they looked at the screen that'd have found the defiance beta, probably crashed again. If they dug around, a shit load of borrowed music, a bunch of movies, and enough porn to fill to either permanently scar the poor bastard searching the computer or turn them into a furry themselves.
They would find I almost only play Crysis/Crytek games, I run about a billion tabs in firefox consisting of about half dealing with nissan trucks and parts, some RC and airsoft related tabs, this tab open and a couple job applications and a couple death metal tabs. Some terrible C++ code, one of which will make the antivirus angry for no reason as all it is a doubly linked list. Lots of music and movies and dragon art ive collected over the years. Then an astronomical amount of school work ranging from word docs to AutoCAd, Creo and Inventor files. Thats about it. Browser history will link to DA, FA, bunch of RC and truck stuff and lots of gun stuff.
Well, lets see, depends how deep they'd look and where, my computer itself has it's fair share of kaiju art pics, some metroid art, mostly from this one person, lapfox art and my own art. And some pics of sergals and nevreans, some naughty ones like rain and such. Whats funny is I thought of this from time to time, very amusing to picture what my parents would find.
NINE FUCKING GIGABYTES of pone pics and arts. Surprisingly none of it nsfw.
But I've got a folder full of the fucking strangest anime porn I've dredged from the depths of 4chan. Solely for the lulz, of course. There isn't a single picture in that folder that won't make you question your own sanity and/or laugh until you throw up. That might raise some red flags.