What are some fun outdoor (night time) games to play with a large group of teenagers in a very big area?

Man hunt is always fun.

Flash light tag... I personally like a good game of hide and seek... But in teams and the 'losers' have to do something totally outrageous or a scavenger hunt, there all al minds really too many to list here

capture the flag, a game where one person is it, and people have to join them. try some camp games http://www.ultimatecampresource.com/site/camp-activities/large-group-games.page-1.html

Sardines. This one is ALWAYS the best!!! One person goes and hides alone, and after the group is done counting they try to hide with that person. You don't want to be the last one not hiding. And, when it's dark it's even better because the goal is to secretly hide with the hider so no one knows you're there. Tough to explain, sorry!(:

Spin the bottle

omg, truth or dare! duh! how did no one else say this???? or if your really daring try 7 minutes in heaven!:)

Marco Polo. Hide and go seek Tag is fun! If you know where a corn field is, try hide and go seek in that, or tag! And last but not least, Armies! You can march, run, roll, crawl, hide, spy, confuse players, its the best! Happy Birthday and good luck!