I think everyone has different playstyles - do you want a team or solo scrapper? AoE or Bosskiller? How expensive will the build be? The synergies of various combos depend on what you want.
My personal quick overview:
Shield is the "best" secondary. It's got great defenses and offense.
Willpower is generically useful and easy to level with, goes great if you want an "invisible" secondary.
Fire does the most damage, but the tradeoff is to be a little more squishy.
Those 3 are my favorites, mostly because I like damage causing energizer bunnies. I think WP is superior to Regen.
Primaries:
Spines for AoE.
Fire for best damage overall.
Dark is nice damage combined with added survivability.
Katana, Claws, MA and BS for solid single target.
My DM/Shield was built for damage and could still tank for a TF. Might have been my best overall toon, but he was uber expensive.