One hit kills/fatalities:
These codes are for the default settings...
Key:
T= press the direction towards your opponent
A= press the direction away from your opponent
LP=C-Left
RP=C-Up
LK=C-Down
RK=C-Right

MinaTek: T-A-LP+LK (close)
ZipperHead: T-A-A+RK (close once opponents arms are gone)
Ssapo: T-A-A+RP+RK (close)
PsyClown: T-A-A+LP+LK (close)
Sabotage: T-A-A+RP (1-3 steps away once opponents arms are gone)
BullzEye: T-A-A+RP (close)
Delta: T-A-A+LK (close)
Purge: A-T-T+RP+RK

Taunt:
To taunt your opponent, press LP+RK simultaneously.

First-person fight view:
To switch into a first-person fight view press and hold left on the digital pad and then press the start button. To switch back, press and hold down on the digital pad and then press the start button. The code can only be performed once a fight has started.

Thanks to Revolution readers The Wizard, Kevin Quillen, and Dave!