Sentir
Cela ne sent pas bon = (fig.) I don’t like the look of that.
Je ne me sens pas de joie = I am beside myself with joy.
Service
Qu’y a-t-il pour votre service? = What can I do for you?
Servir
Madame est servie = Dinner is served.
*À quoi sert de vous mettre en colère? = What is the use of getting angry?
Seul
Cela va tout seul = That is no trouble; That works of its own accord.