Final answer:
Use a hairdryer or a heat gun to safely remove ice from a sight glass, as these methods apply gentle heat to melt the ice without damaging the glass.
Step-by-step explanation:
To effectively remove ice from a sight glass, the most suitable tool would be a hairdryer or a heat gun. These devices gently apply heat to melt the ice without causing any temperature shock or damage to the sight glass.
Using warm water could potentially cause the glass to crack due to the rapid change in temperature and using an ice pick could scratch or break the glass. Therefore, either a hairdryer or a heat gun which will carefully raise the temperature and cause the ice to melt is recommended.