You hear a lot about “that guy”, he pops up in podcasts, people write blog posts about him and GW have even made reference to “that guy” in White Dwarf. However I can't say that I've ever had the displeasure of bumping into “that guy” at a tournament, maybe that's because I spend most of my time playing far away from the top tables but I don't think he's necessarily a top table fixture. Maybe I've just been lucky but I think there's more to it than that.
I think a player's own outlook can greatly affect how he perceives the person across the table from him. So perhaps “that guy” is just a reflection of certain people's perceptions and expectations? A little harsh and certainly not the whole story but I do think that there's a good chance that some people will meet “that guy” more often than others will.
This may also partly be down to the fact that I expect everyone defines “that guy” slightly differently. Someone may see a MSU Space Wolves player and immediately label him “that guy”, alternatively it may take another player to have to cheat or do something blatantly rude before his opponent would remember him as “that guy”. Is “that guy” a win at all costs gamer or someone who is just genuinely unpleasant?
For me “that guy” is just someone who I really didn't enjoy playing against, not because I lost or because he played a tough list but just because he didn't make the game any fun for me to play. I expect this is a common definition for “that guy” but what makes an opponent fun to play against is a personal thing and is going to be different for different people hence my comment above about him being a reflection of a person's own opinions.
So after all this pontificating I think I must conclude that “that guy” doesn't exist, he's literally a figment of your imagination. I'm a firm believer that you are in sole control over your own emotions so your opponent shouldn't have any effect over your enjoyment of the game. Play it how you want to and make sure you enjoy it!
Uh oh! I'm doing the BOLS “change-the-colour-and-ask-the-audience-a-question(tm)” bit. Have you ever met that guy? Do you think there is such a gamer? Tell us about your experiences and how you cope when you do face off against “that guy”.