I was at networking drinks, chatting to 2 guys I don't know.. then I noticed and eye contacted with a rather handsome guy.. within a minute he came over, introduced himself to the guys I was with and completely ignored me!? Whilst he chit chatted with them!!
Why did he just ignore me like that? Is this common guys?

One girl in particular but then you say he talked to the guys and ignored you.
So you weren't singled out among a group of girls.
What did you want him to do?
Single you out apart from the guys and worry that he might be getting a boyfriend upset?
Yes it is common for a guy to talk to the guys and leave the girl(s) ignored.

Maybe he didn't hear you or he waz 2 shy 2 speak to you