Arcade Mode:
To unlock Arcade Mode, beat the game once through on any difficulty level.
Arcade Mode itself is split into two options – Full Challenge or Level
Challenge – that add extra replayability to the game.

Intel Pieces:
Below is the level distribution list for Intel Pieces, which are enemy laptops
full of information strewn throughout the game. There are thirty of them total.
The left column is the level in question, while the right column is how many
Intel Pieces can be found on that level. Levels with no Intel Pieces are excluded

Level 2 – 2
Level 4 – 2
Level 5 – 3
Level 6 – 2
Level 7 – 2
Level 9 – 3
Level 10 – 2
Level 12 – 2
Level 13 – 3
Level 14 – 2
Level 16 – 2
Level 17 – 1
Level 18 – 2
Level 19 – 2

Prestige Mode:
To unlock Prestige Mode, which is a multiplayer-only mode, you must reach
experience level fifty-five. Instead of capping out at level fifty-five, which
is the highest level, Prestige Mode allows you to start again from level one.
This can be done a total of ten times, giving you ten different icons in in-game
lobbies to show your extreme achievement.

Exelent sniper spot:

when you playinig pipeline up the hill up the left the should be a big big bottle and go
to that bottle and there you go kneel down up a lot of people go up the hill and near it