Broadly speaking anything that does either a lot of reasonably specialized logic and medium-to-high performance broad work will have an FPGA in it (unless its made in very high volumes in which case it may be an ASIC, ditto for very high performance things).
Some FPGAs are absolutely tiny e.g. you might just use it as a fancy way of turning a stream of bits into something in parallel for a custom bit of hardware you have, other FPGAs are truly enormous and might be used for making a semi-custom CPU so you can do low latency signal processing or high frequency trading and so on.
Some FPGAs are absolutely tiny e.g. you might just use it as a fancy way of turning a stream of bits into something in parallel for a custom bit of hardware you have, other FPGAs are truly enormous and might be used for making a semi-custom CPU so you can do low latency signal processing or high frequency trading and so on.