What would you use it for?
An op-amp is a really effective tool for various analog circuit purposes.
1. Amplification. One unit goes in, ten units go out. Half unit goes in, five units go out. It's really well behaved and pretty much entirely dependent on the feedback resistance, over a wide range of input and output levels.
2. Buffering. One unit goes in, one unit goes out. But, instead of draining power from the source signal, any load you're driving pulls power from the op-amp, and the op-amp can drive all sorts of loads well without diminishing the output.
3. Comparison. If the left signal is higher, output min voltage. If the right signal is higher, output max voltage.
4. Filtering. This needs a capacitor or inductor in electronics. Low frequencies get fed through the op-amp essentially, high frequencies get effectively shorted through the cap, you wind up with a signal without the high frequency noise.
5. Oscillators. You can generate a sinusoidal wave of pretty high quality with the parameters you want.
6. Integrators and differentiators. This opens up the ability to build PIV controllers, which are
really useful.
7. If we can build a chakra capacitor but not a chakra inductor, we can use an op-amp to simulate an inductor.
Source: wikipedia to refresh my memory, electrical engineering undergrad education