[Szlia]

Spike is a pretty difficult role to cast, because it falls into a stereotypical anime character type (along with the likes of Nikki Larson or Cobra) that goes from a tone to another almost instantly. Goofy -> deadly -> happy go lucky -> seductive -> etc...

A solution is to write some aspects off (I don't remember Jackie Chan doing a whole lot of seducing when he played Nikki Larson) or hope you will (re)discover abbilities in the actor you pick. At least, Reeves did some special effect movies with fights and guns and he did some goofy comedies and even romantic comedies... was he good? Well I only saw his "stiff" parts and Spike is all but that, so I can't tell...

EDIT: If I had to make a risky pick, I would go for Adam Brody. Like the part he is tall and slender, he has a detachment and irony about him that suit the part and, as seen in Grind, he has some athletic abilities that could be useful for action and comedy alike. He is also probably a fan of the source material (which can be good or bad...). That said, you don't exactly fill theatres with his name alone.