UnrealSpeccy is a very complete ZX Spectrum emulator.

It emulates virtually all variants of Spectrum computers with read support for the following formats:
SP, SNA and Z80 (all versions, 48k and 128k), TAP, TZX, CSW, FDI, TRD, SCL, TD0, UDI

Write support for the following formats:
SNA (48k and 128k), TRD, FDI, UDI, TD0 (saved unpacked, so expect saved file larger than loaded), SCR, BMP (screenshots), WAV, VTX as well as a disk images converter (emulator can open disk image in any format (TRD/TD0/FDI/SCL/UDI) and save it to any other format.