"Wiedziałem!"

Translation: I knew it!

[Utvideam]

It puzzles me that no express direct objet is needed. I think (not 100% sure) in German, it is always needed: ich wusste es! Same in English (although: I knew! doesnt sound bad to my ear) or Spanish. For instance, in Spanish: ¡Sabía! does not make any sense, ¡LO sabía! does.

[JanKLinde]

In German and English the direct object is needed in past tense, but it can be omitted in present tense: "Ich weiß"/"I know"

[Jellei]

[Utvideam]

Well, that settles it