"Wait for me!"
Translation:Czekaj na mnie!
Actually with this verb, both seem perfectly fine. Even "zaczekaj" from one of the comments below. "czekaj" focuses on the 'process' of waiting, "zaczekaj" and "poczekaj" on the result - you are still there when the person asking you to wait is ready.
"Poczekaj" and other po- verbs often have the notion of doing something 'a bit', 'for some time'. So it works perfectly for "Wait a moment", "Wait a bit".