File manager - Solid Explorer (great file manager in general, on tablets also gives you two panels to work with)
Keyboard - Swiftkey 3 (better than stock in every way)
Social apps - Skype (pretty self explanatory), Flipboard (the best all around reader)
Customization - Ultimate Custom Clock Widget (create your own widgets with ton of options), Minimalistic Text (also create your own widgets but focused mostly on text widgets), HD Widgets (big screen needs some big and hi-quality widgets)
Games - Dead Trigger (despite all the recent BS with the game's developer, it's still one of the best game on Android), Demolition Inc (strategically blow sh*t up), Major Mayhem (simple game but fun as hell), Obscura (fun platformer with great art style), Roboto (another fun platformer), and of course some emulators like SNesoid, Gensoid, Mupen64.
Security - App Lock (protect any app with a password), LBE Security Guard (*root required* permission manager with an easy-to-use interface).
Side note: no, you do NOT need an anti-virus app. Just stay off the Chinese markets and don't side-load shady apps, and you'll be fine.