Assassins: What are they good for?

This morning, I was rethinking the AD&D Assassin class.

It's a popular class with some, hated by others.

JB had a big series about them earlier this year, after he and Alexis failed to come to terms with what the class was for and how it should be played.  As Paladin in Citadel recently pointed out, the biggest trope D&D brought to fantasy was that of the "adventuring party."  With that in mind, what is the point of the Assassin?  How do they best fit into the standard adventuring party?

One of the problems (that also appears with OA games and the Ninja), is that the Assassin in fiction is quite often a loner.  And due to that plus their alignment restriction to Evil, I've often encountered players of Assassin characters who try to hide the fact from the other PCs, and sometimes from the other PLAYERS as well.  I don't remember reading anything in 1E that specifically advises Assassins to hide their true profession, but OA sure does with the Ninja (and the 2E Complete Ninja's Handbook as well).

Screw that.  If you're an Assassin in an adventuring party, you're a useful asset, and shouldn't be keeping it secret from the group (or at least from the other players).  You've got a job to do, an important role in the party.  And it becomes pretty much impossible to perform that role if you're trying to keep it secret.

So what's the role of the Assassin?  It's to perform the "surgical strike."

An adventuring party is in a dungeon, or out in the wilderness, and comes upon a lair.  Who's in it?  Do they have treasure?  Can the party take them on with decent odds to come out alive and with the loot?  Is there an Alpha Monster or leader?  If so, it should be the Assassin's job to set up an assassination of that Alpha Monster/leader, if possible, with the party's help.  Then the party as a whole will have an easier time with the lesser monsters/minions.

I've never actually played an Assassin.  I haven't really seen that many played, either.  And when I have seen them played, usually they end up being sorta second-class Fighter/Thieves.  This is either because they're trying too hard to hide their profession, or else because the player or DM seems to think that the assassination ability should only be used on NPCs between sessions when the Assassin PC can go on a solo mission.

I'm sorta itching to try out an Assassin now.  One who makes no bones about his profession, and is along with the party to try to be the guy who takes out the Bugbear chieftain before the fight starts, to lower the morale and also prevent the biggest, baddest Bugbear in the lair from getting involved in the fight.  With the party's support (scouting by the Thief, spells by the Cleric/Magic-User, diversions created by the Fighters, whatever), it could be a lot of fun.