I find it useful on a Mac to use some of the shortcuts for accents and diacritics in the default US-English keyboard layout, since I occasionally do have to type accented characters, or type text in a non-English language and don't want the hassle of changing keyboard setup or going through the Unicode menu. They all involve holding Option and pressing the key, though (for example, 'à' is Option-` followed by typing the 'a'; Option-e gets acute, Option-n gets tilde, Option-i gets circumflex and Option-u gets diaresis; there are also shortcuts for some common specific characters like ç and å).