I'm curious as to what everyone's favorite expansion is. The only one I have currently is Hostile Acquisitions, and it seems pretty cool, especially the section about creating a memorable nemesis. So for those of you who have more of the expansions, which one do you find yourself constantly going back to?

To be honest, Rogue Trader doesn't have much supplements to chose from, since most of the published books are adventures. So far, we have:

1- Into the Storm

2-Battlefleet Koronus

3-Edge of the Abyss

4-Hostile Acquisitions

My vote is for Into the Storm, since I think it's the most important supplement so far, and if you like the game you should get it as soon as possible. It gives you lot of new equipement, rules and character options both the players and the GM are going to love.

I can't wait for Hostile Acquisitions to come as a PDF so I'll be able to finally see what's inside. So far I've heard it's an awesome book.

Thus far my favorite, though this is coming from a GM perspective, is Battlefleet Koronus. First off I love the addition of Grand and Battle Cruisers and xenos and chaos space ships. With the test game we played my group's favorite thing seemed to be the space ship creation phase (A very nasty Orion Star Clipper modified for stealth). In addition I like the squadron and Mass Combat rules as they allow a different scope of play, which is one of the things look for and I found that for the most part it meshes very well with the Wealth Rating and core mechanics, though i've not had a chance to playtest this yet, and hordes are sometimes preferable. (Thanks to black crusade to making hordes more compatible with non Space Marines.) I am looking forward to Hostile Acquisitions myself and it'll probably be my next purchase.

In order of how often they get used in my games:

1. Into the Storm. The expanded Origin Path, Starships, and Ship Roles are the most important IMHO.

2. Edge of the Abyss. As the GM, this book is super useful.

3. Hostile Acquisitions. Expanded fluff for Cold Trading and the new alternate ranks.

4. BFK is the least useful IMHO. It is a great book, but I find myself using it the least.

Will admit that the expanded origin path was great, and I personally loved the Ship-origin Path as an addedum. Plus Into the storm has rules for an Ork Party game. My group has been talking an all Goff Ork Campaign for years now...mmm.

I own four RT books, Core, BFK, Into the Storm, and Lure of the Expanse. While I very much like the extra ships stuff from Battlefleet, and Storm's Expanded Careers made me happy (especially Navis Scion and Flight Marshall), I gotta say my favorite one is Lure, if only because they give me some advanced Eldar stuff; something the rest of FFG seemed to think we didn't need, especially in DW. Eldar are my favorite race, and the book that stats out for me a full-fledged Farseer, officially, rather than fan-made (though I love me some Children of Isha, too), has to get my vote.

Now, if you want to say "but wait, that's an adventure, not an expansion", then I'll go with Battlefleet Koronus. Some of the cool stuff that you can have done to your ships through there is awesome, even if some weapons burn money like Link's magic armor burns it in Twilight Princess, and Battleships are still off the market, no matter how rich you are. Into the Storm is cool, and as said, I like several of the Extra Careers, and the Vehicles finally having official stats, but it ate up enough space giving me Ork characters (that I would space), and Kroot characters, that I just don't care about, but again, no Eldar (minus their ships, which be cool). Sorry Hostile Acquisitions, I don't own you, so I don't know you.

First Answer: Lure of the Expanse
Second Answer: Battlefleet Koronus
Third Answer: Into the Storm

I like Edge of the Abyss.

It's a very personal choice, because I probably have to accept that Into the Storm is an objectively more useful RT book: it's a weightier tome, with far more material, and is more useful for the mechanical aspects of running a campaign. However, I've always had a soft spot for sourcebooks, and Edge of the Abyss is the closest thing to a fluffy sourcebook available for RT.

They're all good though!