The few bits we do get about Reno in the game are a bit conflicting. Still, any amateur writer worth his salt should be able to come up with some half-invented, mainly convoluted analysis of his personality. And that, my friends, is where I come in.
Aerith: Don't fight here! You'll ruin the flowers! The exit is back there.
(Exit Cloud and Aerith)
Reno: They were...... Mako eyes. Yeah, all right. (To Shinra soldiers) Back to work, back to work. Oh! And don't step on the flowers......
Shinra soldier 1: Hey Reno, you just stepped on them!
Shinra soldier 2: They're all ruined!
Shinra soldier 3: You're gonna catch holy hell!
The first time you meet Reno, he's been sent to kidnap Aerith in her church, where the flowers grow. There are two ways to interpret this scene- either Reno's a complete slob and a klutz who really does care about the flowers but steps on them by accident, or he's a total jerk who mocks nature and Aerith in rather cruel ways. Or maybe it's a bit of both.
Tifa: We have to disarm it! Cloud! Barret! Please!
Reno: I can't have you do that. No one gets in the way of Reno and the Turks...
The first time you fight Reno, he's kidnapping Aeris and destroying Sector 7. It's interesting to note that his loyalty is to the Turks, and not to Shinra. Secondly, he's a downright cocky little bastard. Thirdly, he seems to not mind the occaisonal bit of daring, as he jumps off a huge tower onto a (presumably much lower) helicopter to escape your party. To be fair, the physics in Final Fantasy VII aren't exactly realistic (check out Cloud's hair!) but still.
Reno: Hey, Rude. Who do you like? What are you getting so embarrassed about? Come on? Who do you like?
Again, this really shows the comraderie of the Turks. Also, we never find out who Reno likes, which has led to all kinds of horrible slashy pairings.
Shinra soldier 1: So our reports were right! He IS here on vacation! We've finally found him! Get the Turks here for back-up!
Reno: Right now we're off duty and can't run off to save your butts.
Shinra soldier 1: We know you're off duty, but...
Reno: If you knew that, then don't bother us! Lookin' at you is makin' me sober.
Elena: Reno, do you think that was really such a good idea!? I mean that the way a professional, a Turk would act!?
Reno: Elena. Don't misunderstand. A pro isn't someone who sacrifices himself for his job. That's just a fool.
Reno obviously cares about his job but at some point along the line he's learned to separate work and play. Being a Turk is for him strictly business- he's a real professional. He knows what he can get away with- a bit of attitude, adjustments to the dress code, andhe's not opposed to a bit of liquor every once and a while. He's also quite slick and is in no way afraid to say what he's thinking. He's got a sense of humor...
Reno: You're finally here. We're gonna split into two. You do whatever you want. But don't endanger Elena. Don't worry. We won't do anything to that girl, Yuffie. For now...
...But when he kicks into action, he takes charge and is all business. When Elena and Yuffie are kidnapped, your party teams up with the Turks. His quarrel with Cloud is, again, strictly business- but when he wants something he'll find a way to get it.
Reno: (stepping on Corneo's hands) All right, Corneo. This'll be over quick, so listen up. Why do you think we went to all the trouble of teaming up with those guys to get you...? 1. Because we were ready to die, 2. Because we were sure of victory, or 3. Because we were clueless.
Corneo: Two... Number two?
Reno: All wrong.
(Reno continues to step on Corneo's hands.)
Corneo: No...! Wait, sto......! Aaaaaaaaaa......p...
(Corneo falls to his death.)
Reno: The correct answer was...
Rude: ...because it's our job.
And there we have Reno kicking ass and taking names. He manages to mock Corneo quite effectively, give a simple statement of what he's all about, AND save the day. Plus, he kills someone in a fairly cool manner. Ah, torture! A fine gentlemanly hobby, if I do say so myself.
Reno: A man who is thoughtful of his partners, he pushes himself hard.
The above quote is his profile in Before Crisis, a prequel based on the adventures of the Turks. What fun! But this quote sums up Reno pretty well- he's very loyal to his fellow Turks, if not Shinra as a whole, he's ambitious enough to have been made a TURK, and, what's more, he's competent enough not to get himself killed. Most people consider him the second-in-command, but that might just be because he talks more than Rude.
What this quote doesn't encompass his lighter side- the side that has him forever shown as an intoxicated, chain-smoking womanizer. (Though, nothing but the intoxication is ever shown in the game, it's not hard to get this impression.) Still, the combination of his ruthless dedication to the job and his rather easy-going personality, flippant attitude and mocking sense of humor lead me to believe that he's become someone sure of himself.
Reno knows exactly what he's about and how to get the job done. He's so sure of that he has no problem having a bit of fun.