> Agh! "an universe" "an useful" "an uniform"... I suppose that's right, isn't it?

Actually, no, it isn't. You use "a" before a word that starts with a consonant *sound*, not a consonant *letter*. "Universe," "useful," and "uniform" start with a "yoo" sound. So say "a universe," "a useful (thing)," and "a uniform." And say "an honest (person)" and "an herb," unless you're from Britain and not also a Cockney, in which case you pronounce the "h" in "herb" and say "a herb."

The a/an rule is thankfully one that there are no weird exceptions to -- it's practically never broken, because the rule is unfailingly intuitive. Probably this was because the rule was invented for the express purpose of making the language easier to speak in the first place -- so what sounds right, is.