As far as I know whips are the only melee weapon with a range. I am not asking about weapons with reach as those are understood.
There are two whips, the normal whip which is a exotic one handed melee weapon, and the scorpion whip which is a exotic light melee weapon. A whip's damage is 1d2 Small, 1d3 Medium, and 1d4 Large. A scorpion whips damage is 1d3 Small, 1d4 Medium, and 1d6 Large. I could also calculate HP, weight, and price but again those are easy to figure out.
What I don't know is how the 15 foot range is affected. Under the weapon descriptions, nothing is mentioned for either Small or Large variants of the weapons, granted it's assumed the description is talking about Medium versions since most playable races are Medium, and most rules are written for Medium.
My thought is that the whips' reach is affected by the character's natural reach. So Small, Medium, and Large (long) characters can all reach 15 feet. Tiny characters could reach 10 feet. Large (tall) and Huge (long) characters could reach 20. So basically the whip is granting an extra 10 feet of reach to your natural reach. However I have no proof or evidence of this, and because I have an interest in this, I am also biased towards this answer.