Just to bring us back on topic…
My original question was meant to focus on how to make it into a buffet on the strip faster. Not looking for a comped meal and I understand there are better meal experiences than a buffet.
There were some great responses. Just to summarize for future reference:

Skipping the line because you are a hotel guest
Bally’s: I’ve gotten a line pass just for asking a front desk clerk.
Bellagio: Sounds like they give out buffet line passes to their guests. Might help to sign up for their player’s card or tip the clerk when checking in.
Mandalay Bay: Doesn’t give out line passes to their guests at the front desk
Rio: Mixed info whether there is a separate line for hotel guests but based on a June 2006 trip report, there isn’t.
Wynn: Might be able to bypass if you flash a Tower Suites Room key card

It sounds like it never hurts to ask for a line pass when you check in. And it might be worth asking for a rating during checkout since there’s a possibility of getting a blank line pass or VIP key card.

Skipping the line because of play or status
Aladdin: Gold and Platinum status
Harrah’s (and assoc properties): Platinum and Diamond status
Rio (Carnival World & Village Seafood): Platinum and Diamond status
Paris: Maybe Platinum & Diamond only
Luxor: Your host might give one for the asking.

There doesn't seem to be a somewhat specific definition of the amount of play required to get a line pass.

Skipping the line with a tip
$5 to $10 for most buffets depending on size of party. Maybe $20 for the higher end buffets.
The tip might work better with a casino host than at the buffet itself

Other notes
A comped buffet ticket is your line pass
People with a handicap placard might be able to get into the shorter line.
The Venetian (which doesn’t have a buffet) will require a gold card to skip a line.