Explosive jumping

Grenade Jumping
Grenade jumping, or occasionally known as grenade hopping, is a trick where the player throws a Grenade onto the ground and jumps as it goes off, using the force of the grenade to propel them forward. It is usually done with the Plasma Grenade as the sticking nature is easier to work with. You can get to higher places with this trick. If the player has got the Sputnik skull, grenade jumping will be twice as effective but note that skulls only take effect in campaign and grenade jumping will be normal in any type of multiplayer game.

This can also be done by aiming down with a Rocket Launcher, then shoot and jump at the same time or, if you have an Overshield, both a grenade and a rocket.

(to do this on Xbox Live you need to be host)

Bomb-Box Super-Jump
This is a neat little trick that works best in the multiplayer level Zanzibar. What you need is:

Any kind of gun (except Rocket Launcher and Brute Shot) Those Bomb-Boxes that explode when you shoot or hit them A grenade if you wish An Overshield And yourself!

First, push one or two of the Bombs (no more than two, you will die with three without an overshield) and jump on top of one of them. Then jump and about half a second after you tap the jump button, shoot the Boxes, and you will fly up above everyone! This is useful to get up to high places for sniping, or to kill another sniper. You can also hide some boxes around a corner so when the opponent appears you can give them a nasty surprise.