"Armoured dolphins!", "Rökelaff" (no, it doesn't make more sense in Swedish, honest), "Tonight we roam in hell" (which is actually much more, and much better than just the 300 reference, if you get it), and several other inside jokes mostly.
I also tend to use "metal" and "post-apoc" as substitutes for good or cool. Metal in Swedish then, it's usually pronounced like in english, when it's used to refer to the genre, but it sounds much cooler (and unique and speshul flowery) to use it in Swedish instead, just to see the faces of alternative kids when they register the subtle difference. It's "metall" in Swedish.