We don't have many house rules at my table just yet as the players did more roleplaying that dice rolling, but that might change a bit with the new group coming in.
Regardless, here's what we have so far:
--Every character begins to game with a free second specialization of their choice based on their backstory and GM approval. This occurs before they begin to spend XP. The bonus skills are counted as class skills normally.
This free tree does count toward the multiplier for purchasing more trees.
--If a character wishes to purchase a new skill or talent tree, they must find a way to learn the tricks of the trade by another. This can be from another party member (i.e. the Pilot teaching the Mechanic how to fly the ship, while the Doctor teaches the Hired Gun to patch wounds).
--Every character begins with an item worth up to 500 credits that relates to their profession, subject to GM approval. Note that this is a SINGLE item, and cannot be used toward purchasing something "bigger."
--Restricted items can be purchased at character creation subject to GM approval (spice is the big one).
--When purchasing a restricted item, the rarity is increased by 2 and the difficulty is UPGRADED (not increased). A despair means the party member has been found out or double crossed in some way.
--The GM has the right to upgrade the difficulty when it is appropriate without the use of a Destiny Point. This is kept in check for exceedingly difficult or dramatic things.
(This one came up when the party had all of the destiny points at the start of the game to promote the free use of points)
--XP is at the rate of 5-10 per session, with a bonus for good roleplaying, acting within the Obligation, or completing major goals.
--XP is usually awarded during "down time." If XP is awarded without downtime, spend them, because clearly you will need them.
--A character may reduce one trait for the XP it is worth at character creation to emphasize a weakness within the character (a talk with a friend to test this lead to a Human with a low Willpower, the Debt Obligation and Greed as a motivation).
--Like HappyDaze, I state that traits upgraded after character creation will increase the related secondary stats.
My notebook also has the same note HappyDaze has regarding hyperdrives, so I guess I'm not the only one!
--Obligation is lowered by good roleplaying that acts to reduce the obligation. Obligation is increased by ignoring opportunities to lower it or by not acting in accordance with it at all.
Example: the characters with Addiction and Obsession always played their obligations, regardless of the roll. The character with the Duty and Criminal obligations acted on them when they came up, but would bring it up from time to time. The character who had Blackmail never acted on it and never brought it up. The first two had a reduction after many sessions, the second two had reductions when they acted on it at great risk to themselves and the party, while the last one got hit with an increase for never bothering with it.
Combat house rules will come about when I have a party that decides to shoot it out more often (my new group has 1-2 Mandalorians; I think this will happen soon).
I am also working on creating house rules for inventing/building, but they didn't get very far due to the game collapsing and my moving.
There was also a mistake we once made during a testing game, where I charged 5x new trait instead of 10x. The players had a good bit of skills and talents but still left their traits on the lower end. I may change the cost at character creation to allow a bit more leeway, such as moving it to 7-8x instead of 10x (anyone who has played 7th Sea knows the pain of spreading 100pts; this game reminded me of that).
Oh, and the last one: first one to the Star Destroyer wins!