My 2 cents, unless you can define precisely what a role player is, it's very hard to say best role player ever.
With Horry, yeah he came up huge repeatedly in this series, but a lot of that has to do with Detroit's style of defense which is based on suffocating interior shot blocking and forcing you to hit jumpers. Horry shot 37% on 3's this year, 44 in the playoffs, 48 against Detroit(nearly the same against Phoenix) and it's because when teams decide how to defend SA, Horry is typically the 4th or 5th concern behind Duncan, Ginobili, Parker(driving) and sometimes Bowen(also a good 3 point shooter).
Horry is a quality player but he's won 6 titles because he's played with 3 of the best bigmen in the last 15 years, Hakeem in his prime, Shaq in his prime, and Duncan in his prime. Rambis won multiple titles too and was the consummate role player, but same thing, you play with Kareem and Magic, you're going to win titles.
Now as to why Larry Brown says don't leave horry open, partly because he's been killing that shot all postseason for sure, but also because it's blatantly obvious that ALL series, Detroit has cheated off Horry and been burned. I can't believe I'm the only guy that keeps saying why are they giving Horry that shot when he can make that shot, make him drive instead?
He's good but I'm somewhat in the middle of Cheese and Elindholm here, he's simply played so many playoff games he's had a lot more opportunities to make huge plays, but I also think it's hard to deny that he has made a lot of big plays, many guys who have that chance don't.
I'm firmly in the non believer in clutch play, but that's in part due to how I define it, which is that a clutch player is someone who ELEVATES his play in clutch situations. I just don't buy it, stats don't bear it out, and if I DID have a player that played better in such situations my first thought would be, why the hell don't you play at that level the whole game so we don't need so many clutch shots at the end of games?
Interesting debate though. Horry has always fascinated me, I always remember when Chris Jackson was at LSU dropping 50 on teams left and right, Horry on more than one occasion completely shut him down when the played Alabama. It was really something to see a guy that size shut down a small guard, when he was young Horry was a special defender.