Another great childhood game to play as an adult. Actually it's well known as a little more "mature" version of Hide & seek. Basically the rules are as the following:

Divide into two or three teams. (three or more teams gets really interesting) One (or two) teams go and hide while the others sit at the Base counting for two minutes to five minutes. To make Manhunt really fun, some hiding spots take time and noise to get into (trees, bushes, port-a-potty, water, etc) so it's good to have a loud radio, ear plugs, or something to obstruct the "looking team's" hearing. Having them all shout each second out works well too.

Once they have finished counting they all go out looking for people hiding. The best strategy for the looking team is to split into pairs and search the area methodically. If they find someone then all they have to do is tag them to get them out- this becomes more difficult if they're up in a tree or running around.

There's two ways of playing for people hiding: they either have to all make it to Base or hide as long as possible. Having everyone going for the Base is nice because it gives both teams a goal and keeps the game more interesting. If the teams opt to play this way then they must also choose a Jail for tagged people to sit at. If someone who hasn't been tagged or hasn't made it to Base tags the people in Jail, then they're all free and they can run and hide again or make a break for Base.

A certain element of trust lies in the game for it is difficult to keep the searching team from specifically guarding the Base or Jail or from peeking while the other teams are hiding.
Team coordination in Manhunt is critical to winning too. Knowing where your teammates are hiding and are going to hide helps keep everyone spread out. Also the searching team calling out misinformation like "There he is!" even though they don't really know where he is helps to spook them to running off. Or the opposite can be true- if they have a good chance of making it to the Base then saying "All's clear over here" and waiting for reinforcements before making your move is often done.