One unique aspect that often surprises me is the 'reservation of benefit' rule. This rule applies when an individual gives away an asset but continues to benefit from it in some way, such as still living in a property they've gifted. In such cases, the asset may still be subject to inheritance tax upon the individual's death, despite the gift. Understanding the intricacies of the reservation of benefit rule underscores the importance of thorough estate planning and considering all potential tax implications when making gifts.