Well, this role hasn't really been available since the death of the 'golden age' of crpgs (since Black Isle/Interplay, Looking Glass, Origin and Troika all died within a few years of each other), but I always preferred playing the guy who can't fight, but is ultra-intelligent/charismatic and just manipulates his way through the game (getting his companions to do the fighting for him, if necessary). Crpgs that did that well were:
- Planescape: Torment - can't entirely avoid combat, but the best way of playing the game is as a combat-poor wisdom/charisma/intellect build, manipulating everybody and everything into doing your bidding without them realising it. Brilliant brilliant game.
- The first 2 Fallouts (the ones by Interplay/Black Isle) were playable with either diplomat builds or science builds. Again, manipulate your enemies to avoid combat, scientifically analyse the Master's plan to realise why it can't work in the long-term, and talk the end boss into killing himself by pointing out all the holes (whether through diplomatic skill or scientific knowledge) in his plans for a 'new civilisation'.
- Unfortunately, Vampire the Masquerade: Bloodlines turns into a combat-fest from about 1/2-way through the game, but before then it has a great combination of urban questing that can be solved with manipulation (you're a vampire, come on, it fits the setting), stealth, technological ability (computer hacking, etc), with combat sections that might be harder for a non-combat class (just like combat classes aren't going to be able to manipulate everyone into doing their bidding in the other areas), but are relatively short and often have means of using your non-combat build to make things manageable (whether that's tricking guards, getting allies, or hacking the computers to turn off the security). In the 2nd-half you NEED a combat skill, and the game takes a turn for the worse due to overlong (i.e. typical of modern crpg) all-combat sections. Still, that just means you need to boost either melee or firearms, the appropriate supporting stat (strength or perception), and some combat-useful vampire disciplines, leaving plenty of points for charisma/seduction/computers/etc (though don't pick the seduction/appearance build - it looks like it would be good, but it sucks compared to the charisma/diplomacy build, both in turns of awesomely fun manipulation of others, and in terms of usefulness). Still a great game, and a good intro for someone who wants to try the older-style crpgs where 'diplomat' or 'manipulative bastard' was often a viable build, because it runs on the source (Halflife 2) engine, and is still very easily accessible for modern audiences.
Definitely get Wesps' patch (one reason why the game wasn't the all-time megahit that it should have been was because it was so darn buggy until the community fixed it).
- with KotoR2 it's almost impossible NOT to be strong in combat, but you're missing out on most of the game if you don't put major points into diplomacy and/or tech - seriously, you'll miss out on most of the game's story and content if you just blunder through fighting stuff. But that's kind of the point - I can't say more without spoiling things, but let's just say that it plays with crpg conventions in a rather nice way, particularly the odd willingness of random strangers to join your party and obey your commands. Weird how that happens in party crpgs, hey? Almost like you're...taking control of their minds or something, without even you realising it

(ok, that's a spoiler, but nowhere near as big as it sounds). Again, DEFINITELY download the restoration patch - Obsidian are top of the field when it comes to writing good plots and experimenting with different mechanics (sometimes it works, sometimes it doesn't, but you have to give them credit for always trying something new), but tend to suck at both deadlines and bugs. LucasArts also screwed them by giving a then inexperienced company (it was the first game they made) only 12 months to make the game, and pretty much forced them to put it out incomplete, despite it only needing really one more month of work to finish up some of the interlinking questlines and stories (and to give an actual decent ending). Without the patch, it's like watching an awesome movie, only to get to the climax and suddenly have the reel burst on fire. Fortunately, a great deal of the material they were going to implement was left in various directories, and a community team did an excellent job of restoring them.