さ(あ)
Usage
さ occurs after phrases, clauses or sentences in very casual conversation. One function is to catch the hearer's attention, but it is also used as a filler with no meaning.
Examples
レストラン、予約しといたからさ、７時にきてね。
I want to reserve the restaurant, so come at 7 please.
キムさんってさあ、フランス語ベラベラなんだけど、日本語も上手なんだってさ。すごいね。
You know, Kim-san is fluent in French, but I heard they're also good at Japanese. That's amazing, right?