OSLO, DEC. 10 -- The pope almost always gets proposed. There is usually a long list of politicians from around the world, some of whom see the prize as a sure-fire image enhancer, and the American president of the day is generally good for a sheaf of nominations.

But this year's early rumored favorite, Irish rock singer and famine aid campaigner Bob Geldof, did not even make it onto the short list that included eventual losers Corazon Aquino and Nelson Mandela.

The 1987 winner of the Nobel Peace Prize who received the award here today, Costa Rican President Oscar Arias, was a shocker whose name had rarely come up in the fevered speculation that sweeps this small, cozy capital in the weeks before the annual October announcement. That, noted the Norwegian prize selection committee with satisfaction, was how it should be.

The committee, consisting of six prominent Norwegians appointed for renewable six-year terms by their country's parliament, never talks about its deliberations. Chairman Egil Aarvik, 75, acknowledged, however, that making the first cuts from the annual list of 80 to 90 nominees is easy.

Who have been some of the more obvious rejects for the 86-year-old prize? Aarvik demurred, pleading the longstanding tradition of secrecy. When pressed, he strained for a cooperative but diplomatic reply.

Rudolph Hess, he said. Hitler's former lieutenant, arrested during World War II when he landed in Britain on a solo "peace" mission and imprisoned until his death this year, can no longer be embarrassed by the revelation. But who would have nominated Hess -- not once, but several times during the past decade? That, Aarvik responded, he could not say.

With the awarding of the prize today to Arias, for his peace initiative in Central America, the committee begins its only inactive period of the year -- the time preceding the Feb. 1 deadline for nominations for the 1988 award. Already, the rumor mill has begun promoting President Reagan and Soviet leader Mikhail Gorbachev for the agreement they signed Tuesday eliminating intermediate-range nuclear weapons.

But while Aarvik hailed the agreement, he indicated that the committee was in no hurry and would closely watch the progress of the arms-reduction process. "If Gorbachev and Reagan now really reach agreement on throwing away half of the atomic nuclear weapons," a reference to upcoming East-West talks on long-range weapons, "then of course they have accomplished something very, very big for mankind," he said.

"I think you will understand I cannot now even think about next year," Aarvik said. "But I can very well see that such a thing is a natural. We'll have to wait and see."

The committee, he said, would not be rushed. Nor could it be lobbied, something that Argentine dictator Juan Peron learned in the 1940s, when boosters reportedly bombarded Oslo with testimonials on "Peron Peace Prize Committee" letterheads.

As with many past winners, particularly those such as Arias whose achievements are the subject of some international political controversy, this year's award has again raised the question of why six relative unknowns from a small Nordic country should be entrusted with awarding the uniquely prestigious prize.

The controversy about the Nobel committee's composition also arose in 1973, when secretary of state Henry A. Kissinger and North Vietnamese leader Le Duc Tho won the prize for their Vietnam peace talks, and in 1978, when Menachem Begin and Anwar Sadat were awarded for the Camp David agreement ending 30 years of war between Israel and Egypt.

With the exception of noncontroversial winners such as Albert Schweitzer and Mother Teresa, most peace prize awards in recent decades have offended somebody. The 1983 prize to Lech Walesa, leader of Poland's dissident Solidarity movement, seemed to critics to be confirmation that the committee was reflecting the pro-West values of Norway, a member of NATO.

Other critics question the fact that Arias won the award for a peace plan that did not exist at the time of the Feb. 1 deadline. Arias had been nominated by Swedish legislator Bjorn Molin based on previous, unsuccessful efforts to work out a Central American peace accord.

Although Reagan administration officials largely held their tongues in public, they were known to be less than pleased with the award to Arias, whose Central American initiative calls for an end to U.S. aid to the Nicaraguan rebels, or contras.

"I think the same question could be raised regardless of what committee you had," Aarvik said. "Some say it should be an internationally composed committee," an option he believes would cause more controversy than the current arrangement. "If you hadn't had any protest or troubles before," he said, "you would have it then.

"First of all, who would pick the members? Would it be by agreement of all the countries of the world? It would never work."

Aarvik said the committee members were "well aware that the peace prize has political implications." But if they are to keep to the rules that say the award should go to a person or group who has most contributed to "fraternity between peoples" or the reduction of "standing armies," he said, "you can't always get a Mother Teresa.

"Our committee of course is not perfect," Aarvik said. "What we know about the world is limited, of course. We try to the best of our ability to keep informed."

In addition, he said, "we have consultants, and we also take trips."