Arranged by exhaust brand/type (and otherwise no particular order):
Signes - Akrapovic Evolution
MilehighM3 - Akrapovic Evolution
jzbm3 - Akrapovic Evolution
Zettabyte - BMW M Performance
bkitchener1 - BMW M Performance
JABSprings - Eisenmann Sport [with HFC?]
llis - Eisenmann Race w connecting pipes
baliano - Eisenmann Race w connecting pipes
SlamMan - Eisenmann Race Axle Back
dnvrdrvr - Gintani Race axle-back
Matterhorn - Megan Racing cat back
xSOULJAHx - Meisterschaft GT2
TQPDWN - Meisterschaft GTC Titanium Exhaust with SS pipes
maesd74 - Turner Test Pipes
M3Denver - Turner test pipes
DiavelM3 - OEM + Fabspeed X-pipe w resonator & secondary cat delete
E92_SID - OEM exhaust mod
SAINT VAN ROCK - OEM exhaust mod
Skooterbrah - OEM exhaust mod (AR Design) + AR Design X-pipe w resonator & cat delete
ColoCane - OEM
This list is still definitely short.