I did some Googling and apparently there are several of these frequencies in use for air-to-air chat, similar to the way civilian pilots use 123.450 MHz and 123.475 MHz.
They include, but aren't limited to:
234.500 MHz - "Straight"
234.550 MHz - "Straight 5"
299.500 MHz - "Cheap Suit"
300.600 MHz - "Thirty aught Six"
303.000 MHz - "Thirty Thirty" "Winchester" or "Three Oh Three"
303.050 MHz - "Winchester 5"
333.000 MHz - "Triple 3”
333.300 MHz - “Quad 3”
333.550 MHz - “Full House”
345.600 MHz - "Straight" (see also: 234.5 MHz)
351.000 MHz - Haircut
357.000 MHz - "Magnum"
384.500 MHz - "Pistol"
399.950 MHz - "Penthouse"
It seems like specific units have others, often nearby these (for example, there's a "Magnum 5", 357.050 MHz), and others. Of course, there are the specific units' present channels, often referred to us "push 3" or "button 3" for preset 3, for example. There's also the 137-144 MHz and 148-150 MHz ranges for AM air to air voice.