The TI-83+ is the standard grapher of the Math Department. The classroom presentations will cover the correct use of the TI-83+ or the TI-84. Other graphing calculators are available on the market at lower and higher price points. The other choices out there are NOT recommended unless strong, external support can be found on how to use one of them for homework and in-class lessons/tests. The classroom teacher will focus on using the TI-83+ or the TI-84.
In some high level classes, programmable graphers with specialized applications will NOT be allowed unless they are available to every student [and the teacher].