Don't forget to correctly italicize
FIRST.
And you forgot a major one while designing your robot...
K.I.S.S.
And since Nats. is no longer accepted (by most) for shortening The Championship Event, and since The Championship Event takes so long to write

... I just use ATL too abbreviate Atlanta when talking about The Championship Event.
(as do some others as well)
Year specific ones can include IR Sensor (Infrared Sensor) & CMU Cam (Carnegie-Mellon University [developed] Camera)
Some other random ones:
DK: Dean Kamen
WF: Woodie Flowers
DL: Dave Lavery
Manch-Vegas: Home of
FIRST HQ; Manchester New Hampshire.
HQ: Headquarters
Robot specific (or product specific terms can be) ones can be:
RC: Robot Controller (goes on the robot)
OI: Operator Interface (goes in your driver's station)
PSI: pounds per square inch (Pneumatics)
80/20: A company name that makes extruded aluminum and the products that are used with it. (brand name)
AM: (AndyMark)
RPM: Revolutions Per Minute (of the shaft coming out of your gearboxes or motors)
There are a ton more.. but those are the more common ones I can think of.