This isn't a 'top 5' but I'll list down my favorite apps for each category.

RSS reader - Pulse News Reader and FLUD works best for me. Simple and fluid, especially the former. Also get Times if you prefer the 'newspaper' view.

Facebook - Friendly Facebook Browser's my current favorite, especially notable for viewing photos on FB. I quite like Social as well but it's too Flipboard-y for me.

Games - Scrabble and Plants VS Zombies are must-haves. The infinite replay value alone justifies the asking price for me. Geometry Wars : Touch and Labyrinth 2 are also noteworthy mentions. For more than casual gaming, I'd recommend Monkey Island 2 : LeChuck's Revenge and the recently-released GTA: Chinatown Wars.

Photos - Wide Angle is pretty awesome, along with the free Guardian Eyewitness. Thousands of hi-res photos from around the world.

Media - StreamToMe, a PC-to- iPad media streaming application and CineXPlayer, for easy video transfers to iPad.

These come to mind when I think of 'favorites'.

Apple's official policy is to never allow apps which contain explicit nudity. Which is sensible because the App Store would've been overrun with porn, I'm pretty sure. You'd have better luck with the Android platform, if that's the kinda thing you're looking for.