A single parametric EQ allows you to set not only the amount of boost or cut, but also the center frequency and the bandwidth. With experience, you can learn where to apply some boost to help an instrument cut through the mix or achieve a fuller sound. To minimize the filter's effect on the rest of the sound, you can use a small bandwidth. You might be able to control the feedback with a graphic EQ as well, but if its bands are quite wide, you will be cutting more of the sounds that you do want to be heard. The shelving and peaking filters are essentially specific types of parametric equalizers, at least mathematically, but most commercial products do have limits on parameters available.
Many amplifiers have 'presence' knob as part of the tone control system.
This is simply a boost in the mid to high frequencies, say from 2 to 6 kHz. This control is said to alter an instrument's sound on a recording to give the impression that it is actually in the room with the listener. It can also help an instrument stand out more in a mix. Although speaker crossovers are not really a type of equalizer, we've pretty much covered the necessary concepts here. It's very difficult to design a speaker and cabinet that has a nice flat frequency response over most of the range of audible frequencies.