A deer runs into the road and a driver swerves to avoid it, hitting a guardrail. Which coverage applies?

This is a collision claim. COLLISION covers damage from impact with another vehicle or object — hitting the guardrail is a collision. COMPREHENSIVE covers damage from a deer STRIKE (the vehicle hits the deer). Swerving to AVOID the deer and hitting something else = collision. This is a classic and frequently tested distinction: deer contact = comprehensive; everything else that results from avoiding the deer (guardrail, ditch, rollover) = collision.