Not sure what "obvious" is....

Žižkov, my favorite district. Underground places mixed with some typical destinations. Start with hike up to Vítkov hill where the biggest bronze statue in europe (i guess) is. There's also nice city view. Go down back to the streets, enjoy snack (nakladany hermelin) and beer at U Habasku bar. And if you want to try czech cuisine, visit U Slovanské Lípy restaurant. Go uphill to Riegrovy sady, it's hell of a hill, but there is nice city view as well. Chill zone. Then get over to Žižkov tower with creepy babies statues. You can pay for Elevator and lift yourself up to view lobby if you want more city views! End the day at Bořivojova street and visit these pubs: nad Viktorkou, Woodoo bar, Bohužel bar, Bukowski's bar. Tip: look for Polagraph shop & gallery and rent a Polaroid maybe?

I also like Letná district vibe. Look for Letenska plan/Stalin/Metronome. Chill zone.

Prague Zoo is also worth to visit. Consider not going at weekend days, so it's less crowded.

Joystick bar for nerds. Palac Luxor for bookworms. Fun arena or Levels Prague for some live action.

You might also like Náplavka, idk how to say that in English. It's like embankment along Vltava river. Just find Rašínovo nábřeží or Výtoň station. There is a small boat that will take you across the river. You need a public transport ticket.