While using Rikaichan, one invariably notices all the words just consisting of one kanji character with its onyomi reading. However, most of these words seem to be barely used (at least in real conversations). It seems to me that most are only used in scientific papers as abbreviations for the respective jukugo of the same sense.
One character kanji words that are actually usable in conversation (and that don't make you sound super scientific) seem to be 敵, 詩、毒 and 罰, for example. I think I've also heard 地, but there are other synonyms whose usage is definitely preferred. Furthermore there are some kanji that only seem to be used in fixed expressions like 気 in its various idioms and 念 in 念のために(so they don't really count here).
So, how should I think about these words? Are they just newspaper abbreviations (much like 独 for Germany, etc.) that shouldn't even be considered as real words? Are there any general guidelines which words one indeed can use in conversations (Or maybe even an explicit list of all such words which are common 話言葉、since there seem not to be too many)?