HTPC submerged in mineral oil
I really like Bioshock on the PC and played the game extensively. It was one of those games that was a lot of fun, but had me jumping sometimes when scary stuff happens. Another dude, obviously a big fan of the game as well, has taken his fresh HTPC and put the hardware into a new casemod with a Bioshock theme.
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The dude mounted the Atom-powered mainboard and PSU to a piece of clear lexan and shoved it inside a 5-gallon aquarium. He then submerged the works for the PC under 4-gallons of mineral oil. The only component not under oil was the HDD.
He used a bubble filter, black gravel, and some other stuff from the pet store to round out the underwater Bioshock theme complete with a Big Daddy figure standing guard. That Big Daddy figure was purchased from Amazon. The whole thing is very cool.