Interest rate decision
The outcome of the meeting where a central bank sets its policy rate; the macro event with the most direct effect on a currency's value.
A high rate makes holding that currency attractive (carry) and generally supports its value. But the market prices decisions in advance, and when a decision holds no surprise you often see "buy the expectation, sell the fact" behavior.
Banks to watch: the Fed (USD), ECB (EUR), BoE (GBP), BoJ (JPY) and the Central Bank of Turkey (TCMB, for TRY). TCMB decisions are announced on Thursdays at 14:00 Turkey time (UTC+3).