A Rosh Yeshiva friend of mine pointed out three different approaches to this issue, and explained that as a general rule;
1) The Hungarians focused primarily on Halacha and ruled (paskened) directly from the Shulchan Aruch.
3) The Sefardim ruled on almost any source that related to the question at hand, whether is was Gemora, Shulchan Aruch or even a view of a Rishon or Acharon.
Although I know there are exceptions to this, I found this breakdown enlightening as it shows the various approaches to what is considered the 'key' body of Torah literature.
Another friend of mine referenced an anomaly that has become somewhat prevalent today;
In some (neo-mystical?) groups, they rule directly from the Zohar. I know of people who are not as diligent with regard to kosher observances because they claim that mystically only meat requires extreme kosher diligence. They would, for example, permit falafel to be eaten even in a non kosher venue, disregarding all auxiliary issues of kashrut (such as heat transference, vessels, knives and spices etc). Disconcertingly, many of them have the appearance and apparel of regular frum Jews.
This again emphasizes the importance and imperative of a solid grounding in the fundamentals of Yesodei HaTorah.