Of course, there's the relative merits and flaws of the basic fighting skills. Small arms is a solid standby, though it does little for you by game's end in Fallout 1. (There's always something powerful and effective to be found for any skill in Fallout 2.) Big Guns is fun, and on a critical hit it seems unusually likely to utterly eliminate any opponent these guns hit. Throwing sucks.
However, sometimes your AP doesn't allow you to shoot twice, but might allow an interesting combo attack.

So far, I've had fun with two fighting styles.
1) The Forge.
Fast Shot, a Flamer in one hand and a Super Sledge in the other. A close-range combination, but it's not hard to hit an opponent with the flamer, then slap him away with the Super Sledge. These are also pinnacle weapons in their respective skills.
2) Yari.
Discovered while satisfying myself that Throwing sucks, this works best with Slayer, high skills in Unarmed and Melee, just the right amount of AP to be relevant, and a curious attachment to spears. At 11 AP (10 Agility, 1 Action Boy) and Bonus HtH Attacks, I've found I can splatter even Deathclaws with hand and spear, sometimes without taking damage, despite to-hit chances as low as a base of 80 and 90 before the copious modifiers. Spears being a one-handed weapon, they benefit from my poorly min-maxed character's One Handed trait as well.
This usually consists of striking at an opponent's leg to knock him down. If he doesn't go down, I try a spear thrust at the leg, then I thrust the spear into the target's eye or head. Slayer usually ensures any hit to the leg will knock the opponent down, with rare exceptions.
No, this is not meant to be practical. The Forge is practical. At level 20 I do not recommend having combat skills this low, nor to have 200% in Throwing, the situation which led to these low skill. Slayer can make anything effective. But this is fun, something I needed very much after playing this character so long. What this is really about is having fun with spears. :)

I'm sure there are fun combo techniques I've not yet seen. When you guys mix and match, how do you do it?

I never really set out with a particular style in mind during my first playthrough of Fallout, it just sort of developed that way. I never invested points in either energy weapons or heavy weapons, simply because I was just investing in other things. I've never been a fan of heavy weapons anyway, particularly the flamer; the heavy ammunition makes it harder to carry around the mass amounts of loot that I hoard.
I only really used small guns and melee weapons, usually the spear. When I lost my .223 pistol to a glitch I switched to the Sniper Rifle, and it was more than effective. I had pretty much no trouble at Mariposa, was able to clear out full rooms os super mutants while barely getting hit simply by keeping some distance and aiming at the eyes. One hit kill most of the time.

i normaly fight with big melee weapons and big guns for straight forward and brutal aproach or for varietys sake i make specialist characters or well rounded

I too, occasionally, play a well-rounded combatant from time to time, and like you purely for the fun of it. I've had dedicated Big Guns characters throw points into Melee just to run around with a wakizashi.
I suppose that implies, rightly, that my most well-rounded characters are in Fallout 2.