Winning the race became his obsession. (Gerundive phrase serving as the grammatical subject.)Beware the fused participle. Consult the section on Verbs in Parts of Speech on Grammar.com for a thorough discussion. Click here for the beginning of that discussion.
I like swimming. (Gerund serving as the direct object of the verb like.)
He perfected his technique of swinging the golf club. (Gerundive phrase serving as the object of the preposition of.)