I've played many times through with all different sorts of combinations and tactics, so I'll list the last two:
1) Guardian/Jedi Master
2) Matuaki Apprentice->Grey Jedi->Ossus Keeper, with the Circlet of Saresh, and other stat-boosting gear as I came across them. I have an energy shield in one arm slot, usually using them from weakest to strongest over the course of the game.
3) Single green saber. I typically upgrade my sabers with the best Fencing Emitter and Diatum Energy Cells, and Adegan Lens. I always use the <CharName> Crystal somewhere.
4) Usually Shii-Cho, but Makashi vs. Nihilus, Sion, and Traya. I usually used the Master Flurry combat feat when engaged in melee combat.
5) I almost always use Master Speed as my first action in combat. Late in the game I used Force Enlightenment for Master Valor and the armor power, but I find that they last too short a time to bother with them for most of the game. My typical strategy involved Mass Stasis followed by closing in and using the saber, though I would of course switch it up with Force Wave from time to time. For droids I usually just spammed Destroy Droid.
1) Guardian/Sith Assassin
2) Jal-Shey Neophyte Armor->Dark Jedi Master Robes->Dark Padawan Robes (because I like the way they look). Got lucky and found the uber all-stat boost implant. Otherwise I typically tried to use strength-boosting gear.
3) Regular red saber in the main hand, short red saber in the off hand. The off-hand saber had the <CharName crystal>, while both used Nextor Crystals for the Keen effect.
4) A little bit of eveything. I used Soresu a lot once I had it, and Shien against the melee-oriented baddies. For melee feats I utilized both Master Flurry, and Master Critical Strike when I felt like it.
5) Master Speed followed by Master Force Jump. Since every attack from a Force Jump counts as a Sneak Attack, the dual sabers with the two bonus attacks from Master Speed were devastating and killed pretty much everything with a single jump. If there were a lot of enemies, I would use Insanity first, and then force jumps and flurries.