some fairly nasty toys there, before you buy a purpose built weapon to carry around i would reccomend you consider carrying something innocent such as a sturdy pen, AA maglite, marker pen etc that can do the job of a kubotan with the added bonuses of being legal to carry anywhere and have their own uses.
but if you do have your heart set on buying one from this site
ninja spike keyring: would be the most vicious - bottom spike would puncture skin and flesh, the two spikes would do likewise, all points on this would cause a lot of tearing, this is like a combination push dagger and spike.
the ninja spike is recognised everywhere by police, you will have no chance trying to tell police that its just a keyring, in the event that you have to use it, you will very likely cause grievous bodily harm - possibly death, and it will not look good for you. - its your choice wether you want to run that risk - a more dangerous self defence item in exchange for possible legal problems.
The spiral also has this spike, the advantage to the spiral is the grooves in th handle providing a more secure hold for your hand - your fingers would fit in between the grooves - this would prevent your hand slipping if you rammed it into somthing.
the bottom kubotan is also spiked - probably wouldnt have the same grip as the spiral, but is essentially the same thing, a spike
the metal and wooden kubotans will cause damage, but unlike the others they arent stabbing/thrusting weapons - these are what you would use if your intent is control (which is a hotly debated topic in itself in the consideration of self defence)
the most important thing to have in mind is when it is appropriate to use a weapon, only do so when you feel like you are in genuine fear for your health or your life. dont take it out to play with it, dont take it out if you arent prepared to use it.