Everyone knows about
Suzaku's famous spinkick. What isn't known is why he has to rotate his entire body in order to kick someone.
It's Elementary Physics, my dear Watson.
The force at which one object strikes something depends on it's mass and it's speed.
For example, a small rock probably won't kill you if it hits you, but a semi truck will, if they're both traveling at 100 miles per hour. However, a semi traveling at 5 mph won't kill you, but a rock traveling at 500 mph could. Either the object has to be massive enough or traveling fast enough to do damage.
That's why most people would be scared of being beat up by a guy that's 250 pounds of muscle, and not of some scrawny 100 pound nerd. The muscle guy has mass behind his punch, so if he hits you, it's going to hurt. HOWEVER, people in martial arts are taught not to use mass, but speed to attack their opponents. You could take that 100 lb nerd and if he hit you with enough speed, it would hurt just as much as the big guy hitting you.
How does this relate to Spinzaku, you ask? I'll explain that now.
Let's take a look at Suzaku first. The guy's skinny. I think the only person skinnier than him in Code Geass may be Lelouch. I'm just going to guess here but I think Suzaku is around 75 pounds total (and with this I am going to be killed by Suzaku fangirls XD). He's like the scrawny 100 lb nerd in my previous example, skinny and nonthreatening.
Because of his lack of mass, any normal kick he does would have little impact because he has no mass to give his kicks any force. So he uses the principles of centrifugal force to give his kicks more force by spinning around multiple times before he kicks.
A good example of this may be a figure skater, or someone just spinning around on the ground. When the figure skater tucks their arms and feet in, they spin faster. And if they were to stick an arm out and hit someone with that arm, that person would get bowled over quite painfully.
So in conclusion, Suzaku spins a gazillion times before landing a kick because his normal kicks would be too weak. He's producing more force in his kick by spinning around rapidly and then hitting his opponent with a leg traveling at high speed, with a lot of force behind it.
(and if anyone's curious to where I got this idea, it was while I was bussing tables at my restaurant idea that I thought up all this stuff)