So I would keep in mind he intelligence stat reflects your knowledge about the world, not just thinking ability, and that a 12 in Int is I would think the highest a character could naturally get without intense studying unless you're a prodigy. Anything past 12 in a stat reflects a diligence on concentration towards that stat. While new characters are newbie adventurers they typically have years of experience leading up to this point: you can't just wake up one morning and decide to become a level 1 fighter.

I'd also keep in mind that the Guts you might envision would be a very high level character, whereas level 1 would be Guts at the beginning of the series.

I would go for a great sword wielding fighter that goes into the Battlemaster path and wears heavy armor. You'd wanna max out Str and Con if you can, keep Dex at 10, and fiddle with the mental stats to your liking. You could also go Eldritch Knight as well, which could be more indicative of recent Guts to some degree.

Here's a guide to Fighters.

http://www.giantitp.com/forums/showthread.php?373134-Know-Your-Enemy-A-fighter-s-handbook

Also keep in mind that ultimately you shouldn't let your mental stats dictate your roleplaying. Strictly speaking they just represent your mechanical ability to recall knowledge, perceive/be attuned to the world around you, and entertain/persuade people. If you're 8 Int you don't have to play like a dumb person, rather you could just be someone that doesn't know a lot about politics, religion, etc. (which would be reflected in your rolls), but still be a tactical fighter. If you were 6 Int or 20 Int that'd be a little different perhaps. But ultimately your DM shouldn't ever say "you can't say/do that because of your mental stats" as long as your stats are within the 8-14 range.