All of them, cloud_902.
Hiragana, katakana and kanji. It really depends on the word that appears in anime. I mean, if the anime were to show you a ramen stall in a back alley, you'd probably see something like ラーメン (katakana for "ramen"). Outside a hospital, you're likely to see 病院 ("byouin" in kanji). And... let's see, I'm trying to find an example for hiragana but can't.
The point I'm trying to make is that the Japanese language makes use of all three, so there's no "which ONE", really. You're looking at all three of them. ^^;;