And "affect" is also a noun, although rarely used.
affect: the conscious subjective aspect of an emotion considered apart from bodily
changes; also : a set of observable manifestations of a
subjectively experienced emotion
<patients … showed perfectly normal reactions and affects — Oliver Sacks>
At least this usage of affect carries a different pronunciation. The emphasis is on the first syllable here, rather than the second, making it SOUND like a different word than effect.
But it's still a good rule of thumb.