SPIKE
Spike a.k.a william the bloody got his nickname from torturing his victims with a railroad spike. Although his nickname 'the bloody' isnt quite so gruesome and it came from the fact he told 'blody awful' poetry! 
Spike hasn't always been a kick ass
Kinda guy tho and prior to being vamped by future love interest drucilla he was a shy and quiet poet!!!
At a mere 120 years old which is pretty young for a vampire Spike has killed two slayers and has tried on many occasions to kill Buffy although she always came out on top.
A turning point in Spikes life or should i say death was when he was captured and experimented on by the initiative who left him with a chip in his brain and the inability to harm any living thing.
The chip took its toll on spike and his new found 'good' side caused him to dump love interest harmony and develop a serious crush on Buffy. Spike had his very own buffy bot created to fulfill all his kinky fantisies but it was soon confiscated by the scoobies!!!
Over all Spike is a funny guy with great fashion sense who you either love or hate, personally i love him (a lot) and it would be a shame if he ever got dusted!!!!