Tacher and tâcher
Here are two verbs that should not be confused. Tâcher (to task) means "to make an effort to get something done, to work on a task" while "tacher" (to stain) means "to make a mess, to make a stain".
The only difference between these two verbs is the circumflex accent, so they are not confused. One way to remember this is to say "tâcher de ne pas faire de tache à ses vêtements" (try not to make a stain on your clothes). The first verb has a slightly longer "a".
J'ai une tâche à faire ==> j'ai un travail à faire.
Je me suis fait une tache sur mon vêtement ==> j'ai sali mon vêtement.