From the Arab Spring to the Eurozone crisis, 2011 was marked largely by tumult abroad. But back in the United States, the political scene was no picture of calm.

The year began with the horrific shooting in Tucson, Ariz., that left six people dead and 14, including U.S. Rep. Gabrielle Giffords, injured, and it ended with the last troops coming home from Iraq. It began with Congress deadlocked over spending and taxes and ended with Congress, well, deadlocked over spending and taxes.

In between, we saw Osama bin Laden killed, same-sex marriage legalized in New York, Barack Obama's long-form birth certificate released and the Occupy Wall Street movement founded. The year was punctuated with labor disputes and sex scandals and permeated throughout with congressional deadlock -- not to mention the wild ups and downs of the ongoing presidential campaign, which will be recapped in a separate article.

Here are the five most memorable political moments and trends of 2011, good and bad:

5. Tucson Shooting

When Jared Lee Loughner shot U.S. Rep. Gabrielle Giffords in the head in Tucson, Ariz., on Jan. 8, a little-known congresswoman was catapulted into the spotlight for the worst possible reason. But as the year went on, Giffords' incredible progress turned a tragedy into a message of hope.

The bullet that went through her brain somehow spared both her life and much of her cognitive ability, and today, as the one-year mark approaches, she is able to walk and to understand what is said to her, although she still speaks haltingly. She even hopes to return to Congress eventually: a milestone that had seemed impossible when she was hovering between life and death last January.

Moreover, when she appeared on the floor of the House of Representatives on Aug. 1 to vote in favor of raising the debt ceiling -- her first public appearance since the shooting -- she received a standing ovation from her colleagues, in one of the only shows of congressional bipartisanship all year.

4. Equal Rights Battles

Though many battles remain, 2011 was a watershed year for gay rights, with the legalization of same-sex marriage in New York and the repeal of the military's don't ask, don't tell policy, coupled with ongoing legal challenges to California's Proposition 8.

The New York legislature voted to legalize same-sex marriage in June, after a drawn-out campaign in which Gov. Andrew Cuomo, a Democrat, was instrumental in securing the deciding votes from four Republican senators. With the 33-29 vote, New York became the sixth and by far the largest state to allow same-sex marriage, joining Connecticut, Iowa, Massachusetts, New Hampshire and Vermont.

Three months later, the military officially lifted its ban on openly gay service members, following a drawn-out debate over repealing the 1993 don't ask, don't tell law. While the repeal was widely panned by Republicans, who argued that it would prevent the military from doing its job, a majority of the country celebrated it as a milestone in the slow march toward equal rights for gay Americans.

3. Foreign Policy Victories

While many of Obama's economic policies have been poorly received, he earned praise for his handling of foreign affairs this year, especially his authorization of the operation that killed Osama bin Laden in May. Now, as the world enters 2012, it has two tyrants and one war less than it did at the beginning of the year.

On May 1, Obama called a press conference shortly before midnight and announced that bin Laden had been killed in a raid on his compound in Abbottabad, Pakistan, just four months shy of the 10th anniversary of the Sept. 11 attacks that the al-Qaida leader masterminded. Praise poured in from both sides of the aisle, including from former President George W. Bush. Then, in October, Libyan dictator Muammar Gadhafi was shot and killed by rebels after several months of military action led by NATO and by a coalition of countries, including the United States.

That same month, Obama announced that all United States troops would be withdrawn from Iraq by Dec. 31. The last troops came home on Dec. 12, marking the end of an eight-year war that began on the presumption that Saddam Hussein had weapons of mass destruction and evolved into a broadly defined nation-building mission. Most Republicans criticized the decision to end the war, saying Obama should have left at least a small contingent of troops in Iraq to maintain order there, but there was no denying the historic nature of the withdrawal.

2. Budget Brinkmanship

To say Congress was dysfunctional in 2011 would be an understatement of epic proportions. To put it bluntly, from the debt-ceiling fiasco in July to the super committee failure in November to the payroll-tax battle this month, Capitol Hill was a disaster zone, full of inaction and political posturing.

The Great Budget Crisis of 2011 began in late spring and early summer, when Obama asked Congress to raise the federal debt ceiling so that the government could continue to pay off debts already incurred. Republicans refused to do so unless the increase was matched dollar-for-dollar by spending cuts, while Democrats insisted that revenue increases be part of the equation, and the ensuing deadlock threatened to shut down the government. A stopgap deal was reached at the last minute, but not in time to stop Standard & Poor's from downgrading the country's credit rating for the first time ever.

Then, in November, the super committee established by that deal announced that it could not get past partisan bickering and agree on the deficit-reduction members it was tasked with agreeing on. And no sooner had the super committee imploded than Congress found itself embroiled in yet another budget fight, this time over extending a payroll tax cut for middle-class families.

The cumulative effect of these political games was the lowest approval rating Congress has ever seen: 11 percent.

1. Occupy Wall Street

When it began on Sept. 17, few people thought Occupy Wall Street would last for long. The protesters would take over Lower Manhattan for a few days and then disperse, consigned to the annals of movements-that-never-were.

But something happened that people didn't expect: Occupy Wall Street caught on. The protesters did not leave. They set up camp in Zuccotti Park and stayed there for two months before the New York Police Department evicted them in mid-November -- and after that, they regrouped and continued to organize marches and other actions throughout the city.

More importantly, Occupy Wall Street inspired similar actions in dozens of cities across the country and around the world, many of which are ongoing. In Washington, politicians from both parties have been forced to take sides on the issue of economic inequality, bringing the protesters' talking points into the national spotlight in a way they had not been before. Many people blasted Occupy Wall Street's positions, but nobody could ignore them. Even the people cursing them out were talking about them -- and that was the point. It's too soon to guage Occupy Wall Street's impact on U.S. public policy -- the movement has not experienced even one congressional election yet -- but it is safe to say that the Occupy coalition has changed the political culture in the United States -- it has restructured the debate to the point that income inequality is now on the mind of senators and representatives.