Without any doubts SMC Pentax-FA 1:1,8 31mm Limited is probably the best Pentax lens in this range.
SMC Pentax-FA 1:1,8 31mm LimitedRiomaggiorePentax smc P-FA 31mm f/1.8 AL LimitedPentax smc P-FA 31mm f/1.8 AL LimitedPentax smc P-FA 31mm f/1.8 AL Limited