MechAssault

Unlock Ragnarok
Finish the single player Campaign mode once to get access to
Ragnarok in local multi-player mode.

Unlock Ymir mech:
Finish the game on any difficulty mode to get access Ymir.

Keep Cool:
Jump into a river to cool your overheated wepons.

Cloaking in water:
Use cloaking (turn invisible) when you are in the water. Nobody will
see while walking in the water.

Easy way to win Last Man Standing:
Select minimum 3 players to play. Hide, and then after everyone has
killed the others, come back out and fight the last player
that was standing.

Saving ammo:
Save the short-range missiles for larger targets.
You've got a really limited supply.

Destroy Buildings:
You can find health packs and other items in the buildings. Some of the
buildings are spawn points for tanks and other nasties.

Avoid PPC projectile
If you want play on Xbox Live, select a mech with jump jets.
If the enemy is charging up their PPC, activate your jump jets,
When they fire, release the jump jets and the PPC will fly over
you as you fall to the ground.