I had a merchant character in one of my GURPS Traveller games. He had lots of merchant skills and such, but no shipboard skills. I always thought he would get fairly bored each time they spent a week in jump space.
After a while, I noticed that we never actually filled up the hold on our ship (we had a 400 ton Fat Trader with no subsidy). One time, after the GM awarded XPs, I asked the GM if there was a department store in the Spaceport. Cautiously, he said, "Yes." I told the GM I was spending 100 Credits in the department store on "Character Development" items.
Later when we were all abord ship I reminded the GM of my purchase. I told him I was taking my items to the hold. This got all the characters, and the players, attention. they all followed my character to the hold.
From my "bag" the character pulled a can of white spray paint. The character painted white lines on the floor of the hold. Then from the bag he pulled a tennis racket and a can of balls. I then informed my GM I was spending some of my XPs on Sport:Tennis and that I intended to spend my time in jump space whacking tennis balls against the bulkhead.
The GM was impressed, and gave me an additional XP bonus.