。
I don't think he's a weird guy.
Literal
I [topic-は] weird guy [is-だ] [quotative-と]-[contrastive-は] think-not.
とは is the quotative と + contrastive/topic は, foregrounding the content of the thought — 'as for thinking (that), (I don't).' 思わない negates the whole clause. やつ ('guy, fellow, that person') is casual and somewhat rough. 変な is the attributive form of 変 ('strange, odd'). A defense of someone.