Index Modulation (IM) techniques enable a significant Spectral Energy (SE) and/or Energy Efficiency (EE) enhancement. In this paper, a novel Filter IM domain is being explored, where a novel scheme Filter Shape Index Modulation (FSIM) is proposed. In contrast to most existing Single-Input Single-Output (SISO) IM systems, the proposed scheme achieves a higher SE/EE gain since it exploits all available time and frequency resources. The FSIM system transmits any conventional modulation (QAM, PSK,...) while conveying additional information bits by the index of pulse shaping filter shape. The optimal joint Maximum Likelihood detector is presented, and a low complexity optimal detector is proposed. In addition, an Inter-Symbol Interference (ISI) estimation and cancellation technique is developed to enable the usage of non-Nyquist filters. Finally, the results reveal that FSIM has a similar performance with the two proposed detectors, and it achieves an important performance gain of up to 6 dB compared to equivalent schemes of the same SE in AWGN and frequency selective channels.