Nyquist sampling rate
Implications of the Shannon-Nyquist sampling :

a. Sampling rate below Nyquist rate: Aliasing happens: shifted spectra of the sampled signal will overlap; i.e., high frequency signal content will be aliased into lower frequency regions of the spectrum and low frequencies into higher, therefore, irrecoverable misinterpretations happen about the authentic (true) content of the sampled signal spectrum; 

b. Sampling rate equals Nyquist rate : Depends on the signal type. If there is no impulse at the Nyquist frequency, or the spectrum is zero at the Nyquist frequency, then this will in principle satisfy Nyquist sampling rate, but requires an ideal anti-aliasing filter to be practically implemented and thus usually avoided and a slightly higher sampling rate is preferred instead.

c. Sampling rate larger than Nyquist rate : Satifies Shannon-Nyquist sampling theorem, allowing perfect and unique recovery of the original continuous-time signal from its samples. However, going too high, unless necessary will increase system cost. So practically it's best to limit the sampling rate to a satisfactory minimum or an achievable maximum.