Actually,

does nothing but give you points.

gives you 10 points for kicking the bombs,

just gives you 10 points while randomly walking (no definite period or amount of walking). And finally,

gives you 10 points for jumping.
As for the

, even if it does kill an enemy in the right order, it negates all possibilities for getting the large crystal for the level. Also, from the several levels I've used it on where I know the sequence (with 3 or more enemies, mind you), it almost always gets them in the wrong order.
Furthermore,

isn't as annoying as

. In fact, it helps out a lot more than you realize in the later levels (70+). My favorite item would have to be the ghost candy, which basically makes you the invinsible Pac Man

The best combination, IMHO, is

, in that order. Probably could make do without

, but it's almost indespensable in the later levels.