A positive/negative trait system, where picking negative traits inflicts a malus on your character but gives you some additional points that can be spent on stats, skills or picking positive traits.
Example:
Negative traits:
1] an uncommon blood type (perhaps Rh
-ve) , that could make things
difficult if requiring a blood
transfusion, but gives you
additional points to spend during
chargen.
2] An addiction to easy to find
drugs (like nicotine or alcohol),
that slightly decreases your
stats or skill when in
withdrawal.
Positive trait:
1] Eagle eyed, that gives bonuses to
perception related things, like
medical diagnosis, or increased
accuracy with a firearm, atop what
the stat and skill provides.
2] Naturally large lung capacity,
which is seen in those who’ve been
swimming a long time. Perhaps this
will let them weather strenuous
activity slightly longer than your
average person. Perhaps faster
recovery of stamina.