Oil Slick
Although a little small and pathetic, this lump of oil is actually quite handy for slowing down an opponent. If you catch it on the side or at a funny angle, you can end up facing in the wrong direction, which can be a real bonus if you were the one who dropped the oil slick. Remember that if you drive through it with a shield on, it will disappear, only one person can get caught in it, and after a short time it will dry out and disappear.

Barrel of Gunpowder
This is like a poor quality cannonball which you throw in the wrong direction. Unlike all of the other Hazards, it will target a certain racer and have a similar effect on them to a cannonball (but you don't loose a power-plus brick). I think that they tend to target a certain racer, but it is very hard to test this theory.

Magnetic Trap
Perhaps just as good as a Mummy's Curse, if you drive near this then you will sure be stuck for the next few moments. A shield will protect against it but once it has caught you, I don't think there is any way to get out of it. Trying to drive around them doesn't work either, as they move about a bit.

Mummy's Curse
The ultimate weapon! It has the advantage of getting loads of opponents stuck in one go! If you get caught in one yourself, then reverse the use of the direction keys, so the left button is to turn right and vica-versa. This isn't foolproof but it should help. Remember that if you touch somebody else whilst you are 'cursed', then they get the curse instead!