Personal Actions are performed by pressing HP + HK. When you do a
Personal Action, you gain a small amount of SA power. Some Personal
Actions can hit for minor damage (and a small SA power increase), as
well, and in such cases can be comboed into (try Ibuki's close HP--
cancel the first hit into her Personal Action and it will combo).
However, Personal Actions are there for more than just taunting; they
also offer a variety of benefits:

ALEX His attack power increases. If you hold down HP+HK, it will
begin to increase even more at a steady rate, but after a
certain point you cannot earn any more attack power. As an
alternative, you can simply perform the taunt repeatedly and
raise his attack power that way (it maxes out after four
taunts).

CHUN What bonuses she gets depends on what she does during her
LI Personal Action:

- If she yawns, her stun gauge recovery rate increases.
You can yawn up to three times for increased recovery.
- If she also cracks her neck, her attack power increases
for all moves but throws.
- If she also pats her shoulder, her defense power increases.
- If she also arches forward and stretches her hips, her
attack and defense power increase.

DUDLEY His attack power increases for all of his moves except throws.
His Personal Action can hit, but if you attempt it immediately
after throwing a rose, Dudley merely holds one up. In this
case, he still gets his attack power increase, but he gets no
SA gauge bonus for doing his Personal Action.

ELENA All of her attacks do more stun damage. You can taunt more
than once to increase the amount of stun damage you do (after
four taunts, you won't earn any more damage). Elena's Personal
Action is both a low attack (when she sweeps her leg out), and
it can hit somebody in the air when she lifts herself up.

GILL His attack power increases.

GOUKI His attack power increases for all of his moves except throws.
Additionally, all of his attacks (even throws) do more stun
damage. Note that the Shun Goku Satsu will not do more damage
even if you do Gouki's Personal Action.

HUGO His attack power increases for all of his moves except throws
(this includes all special move and Super Art throws). If you
hold down HP+HK, he does an alternate taunt that also increases
throw damage. Furthermore, each time you do either taunt, he
gets a defense bonus (less damage from attacks). After taunting
four times, you won't get any more defense power bonuses.

IBUKI Her attack power increases. Her Personal Action can hit
somebody, and in fact she won't get an attack power increase
unless her Personal Action hits!

KEN His attack power increases for all of his moves except throws.
His Personal Action can hit twice, but the hits no longer combo.

MAKOTO With Makoto's taunt, you can hold HP + HK to make her perform
three actions. Just pressing it makes her do one action, and
this can hit for minor damage. It also increases her attack
power for all moves except throws. Holding it until the 2nd
action comes out gives her a further attack power increase.
Either action also gives her a stun gauge recovery rate boost.
Holding HP + HK until she does her third action gives her an
additional stun gauge recovery bonus. So basically, let her do
one action for an attack and stun recovery bonus, two actions
for two attack and two stun recovery bonuses, and three actions
for two attack and three stun recovery bonuses.

NECRO His attack power increases for all of his moves except throws
(this includes his Snake Fang, German Suplex, and Slam Dance).
His Personal Action can hit multiple times, and you can hold
down HP+HK to make him keep flailing his tongue at you.

ORO His stun gauge will lower a bit. If you hold HP+HK, he will
continue to sleep and lose even more stun gauge power.

Q He gets a defense bonus for the rest of the round. You can
taunt three times for an even higher defense power.

REMY All of his attacks do more stun damage. You can taunt more
than once to increase the amount of stun damage you do (after
four taunts, you won't earn any more damage).

RYU The rate at which his stun gauge empties will increase a bit.
You can taunt up to three times to increase the rate at which
his stun gauge goes down, but after that point, additional
taunting won't do anything.

SEAN All of his attacks do more stun damage. You can taunt more
than once to increase the amount of stun damage you do (after
three taunts, you won't earn any more damage). His Personal
Action can hit somebody (you can even use it to start combos),
but if you try to throw another basketball after the first one
was thrown, Sean will jump up and panic when no basketball
comes down I didn't notice that much of an increase in
stun damage as I did in 2nd Impact, for some reason.

TWELVE He turns invisible, and remains this way for a limited period
of time, or until he is hit, he blocks an attack, or he
performs a hold or Super Art. Note that he won't turn visible
after parrying attacks, using (or getting stopped by) the Grap
Defense, though. If you do an EX special move, the EX 'flash'
will still appear on-screen. If you use the X.C.O.P.Y. in a
Twelve vs. Twelve match, you won't be able to turn invisible,
even though you're still Twelve. Once invisible, you can press
HP+HK to taunt and reappear.

URIEN His attack power increases for all of his moves except throws.
His Personal Action can hit once. Interestingly enough, if
it hits, he doesn't get he attack power bonus!

YANG His attack power increases for all of his moves, but his throws
only get a miniscule (1 point) increase in damage. His Personal
Action can hit once.

YUN His attack power increases for special moves only, but he gets
a miniscule increase for normal attacks, command attacks,
throws, and Super Arts. If you hold down HP+HK, he not only
continues to spin his hat around, but he gets a damage increase
for _all_ attacks. After a while, the damage bonus maxes out.
Alternatively, taunting eight times will max out the damage
bonus in the same manner. His PA can hit multiple times.

If a Personal Action affects 'all attacks', that includes throws, unless
stated otherwise. When you perform a Personal Action, you keep attack
and stun damage bonuses until you make an attack that hits or is blocked
(it's okay if it misses). So if Remy powered up his stun damage three
times, the next attack that hit would do increased damage, but all
future attacks would do standard stun damage until he started taunting
again. For defense bonuses and stun gauge recovery bonuses, you keep
them for the rest of the round! As a final note, attack and stun damage
bonuses seem to be proportionate to the attack itself. If you get an
attack bonus and do a jab, it won't be that much better than it normally
would. A hard punch or Super Art will do considerably more damage,
though.