Phone, tablet, wallet, MP3 player, compass (I take it literally everywhere) and flip knife or foldable police baton (depending on my mood)
This is all I take with me everyday
But if I knew I was about to go to the forest, I would take extra food, water, clothes to change and map update on my tablet.
Most of the time I won't get lost no matter how hard would you try, due to my visuals skills. I can easily memorise path I took and take it back. But in case I really get lost or go somewhere new, I just boot up OsmAnd+