I would say... Broadsword of the Inquisition, Holy pistol, Corsair's Cutlass, and/or Musketeer's Sabre.
Broadsword for the Voodoo Damage, Pistol for the +3 to silver shot, Cutlass for the damage and boosts, Sabre for the Master's Riposte.

Whenever I'm in an invasion I use the Lost Swor of El Patron. Ghost form helps so much when you accidentally hit sweep and you're surrounded by skellies, and it's an awesome sword. Drain Voodoo is wicked for the witchdoctors and gypsies too. But, if I find a General's Broad, Black Shark Blade, or a Seven Seas Cutlass I would use that, no question. I think Critical Strike would just devestate people during invasions. Now, as for my whole invasion belt...

Lost Sword as Primary- I already explained why this is awesome.

Shadow Stalker Pistol for Secondary- Hex Ward and Infinite steel is killer in this. If I'm gonna be fighting a lot of people, I might use the Shadow Stalker Repeater or Clockwork Repeater.

Harrow Staff as a third weapon- Flaming Skull and Wither can wipe out huge amounts of enemies, no way I wouldn't use this.

Knives Of The Sun Idol/Spell Binder Doll, fourth- Both are just good weapons. :)

I use only three weapons for invasions

the lost sword of el patron-ghost from is great
Mercer's blades- they are great for freezing jolly and keg runners.
Hex breaker musket- hex eater shot is great for jolly. Also with the musket your safe from his attacks because of the range.