Which teams are the world's best at being enemies?

	When David Beckham (right) and Real Madrid meet with Xavi's Barcelona on Sunday, expect fireworks. AP
	REACT: What is your favorite rivalry? Your name: Your e-mail address: Your home town: Make your case:

Two of soccer's best rivalries resume this weekend, and the buzz has already started. On Saturday morning, the Old Firm gets back together as Rangers and Celtic clash at Glasgow's Celtic Park. Then in the afternoon, it's the first Spanish Clásico of the year as old foes Real Madrid and Barcelona get it on.

What are your favorite rivalries? E-mail me in the box on the right and I'll print the best responses. In the meantime, in honor of these two classic, heated competitions, here are my five favorite rivalries in world soccer.

5. Los Angeles Galaxy vs. San Jose Earthquakes

Like any good Southern California-Northern California rivalry, this has been mostly one-way for all 10 MLS seasons, with most of the venom originating from the Bay Area. It got worse this year, when former 'Quakes hero Landon Donovan came back from Germany and signed with his hometown Galaxy. LanDo led L.A. to its second MLS Cup, pulling off a titanic upset of San Jose along the way -- something that's really going to stick in the craw of the 'Quakes faithful. Sadly, this could be the end of the rivalry, as the Earthquakes are up for sale and there's speculation they will move to Houston. No more Landon piñatas at Spartan Stadium? Say it ain't so!

4. Rangers vs. Celtic

The stereotypical soccer hooligan found his legs here in a rivalry that dates back to 1888. It may be the ugliest rivalry in all of sports, and certainly one of its most violent. Simply put, Rangers is associated with a Protestant fan base while Celtic is the Catholic team. In a historic power-keg of a city like Glasgow, that's not a good thing. Massive fights between fans are a common occurrence in Glasgow, especially on game days. Injuries, and even deaths, have become common occurrences historically, even though both have been curtailed somewhat of late. Police now line the streets that lead to both clubs' stadiums to prevent any kind of mischief -- which invariably can't prevent everything.

3. Arsenal vs. Tottenham

It may not be the most glamorous of England's rivalries, but the North London Derby is an institution all its own. The clubs' stadiums are a mere four miles apart, splitting the northern part of the city along combatant lines. The animosity dates back to a sketchy series of events in 1919 that saw Arsenal promoted to England's top league ahead of Tottenham, despite the fact that Spurs had a better season. Supposedly, Arsenal's chairman at the time, Sir Henry Norris, orchestrated the move in a series of payoffs and back-room dealing. Today, Arsenal defender Sol Campbell gets most of the scorn for famously jilting his former club in 2001 when Tottenham tried to re-sign him. You know where you stand when your unofficial nickname is "Judas."

2. AC Milan vs. Inter Milan

The 97-year-old Milan Derby is helped along by the fact that the city's two teams share a stadium -- the San Siro, in the neighborhood of the same name. It was renamed Giuseppe Meazza in 1980 in honor of Inter's star player during the '30s. Not surprisingly, Milan fans still refer to the edifice simply as the San Siro. Inter fans definitely hold a grudge, as Milan has four more Italian championships. The fact that Milan's owner is Italian Prime Minister Silvio Berlusconi doesn't sit particularly well with Inter fans, either. In last season's Champions League quarterfinals, Inter fans, angry that a goal was disallowed during the crucial match, showered the pitch with flares, one of which hit AC Milan keeper Dida square on the shoulder. The game was called with Milan leading 1-0. The Rossoneri ended up advancing to the final, and Inter was punished by having to play its next four European matches in an empty San Siro -- er, Meazza.

1. Real Madrid vs. FC Barcelona

And the Red Sox call the Yankees the evil empire. Real Madrid was the beloved team of a real emperor: former Spanish dictator Francisco Franco. The Generalissimo mandated that the entire country speak Castilian Spanish, quashing any kind of regional pride. His dislike of Catalonia was well-documented, and worse, Franco's soldiers assassinated Barça team president Josep Suñol in 1936 and fire-bombed team headquarters. That turned Barça into proud Catalans' only outlet for their provincial pride and hate for Franco. Barça became the club of the high road, and has ever since been the Red Sox to Real's Yankees (with analogous spending habits to boot).

Now it's your turn. What's your favorite rivalry? Do I hear Boca-River? América-Chivas? Man United-Man City? Fire away.

Best derby in the Bundesliga: Bayern Munich and 1860 -- the ultimate war between the haves and the have-nots.
-- Dieter Kochan, by way of Gelsenkirchen, Germany

One of the strongest rivalries in football is Liverpool vs. Manchester United. The rivalry goes beyond simple sports contests, but goes into an economic and social rivalry as well. When the two teams on the Mersey fight it out, they fight hard.
-- Randolph T., Pensacola, Fla.

The biggest rivalry in England is Liverpool vs. Manchester United. Not only does it concern the two most successful clubs in English football, but it also reflects the rivalry between the two cities in general. They simply hate each other.
-- Mark Hewitt, Essex, England

América vs. Chivas of Guadalajara, whose exhibition match at the Los Angeles Coliseum this past summer drew a crowd of 90,000-plus. This derby is lived very, very intensely all over the world by Mexican-league fans. It drew more of a crowd in one match than L.A. vs S.J. drew during the whole MLS season series of four games. One twist: Chivas is the only team in the world that has created a club policy to only hire only Mexican-born players. They haven't had a foreign-born player since the early '40s, so this rivalry is usually the best Mexican players vs. the best foreign players. They both are on top of list in terms of league titles, with the most recent being won by America.
-- Julio Serrano, Lexington, Ky.

The list you have is a good one but only points out the rivalries based on hatred of the other group. What about the healthy rivalries like Liverpool-Everton, AC Milan-Juventus or such? You've highlighted the bad blood without promoting good sportsmanship.
-- Michael Parker, Torrance, Calif.

Good point, Michael. But that kind of attitude is probably the reason Southlanders are on the soft end of California's sports rivalries.

Brazil vs. Argentina, if you count international sides as well as clubs. Each sees itself as the premier South American team.
-- Joe, Branford, Conn.

Amen, but Argentina-Uruguay is almost as bad.

Dinamo Zagreb-Red Star Belgrade. Some serious scholars argue that the war between the Croats and Serbs "officially" started on May 15, 1990, when their match was canceled before the opening whistle. Moreover, this was where Zvonimir Boban became a national hero by dropping a Communist Special Forces member with a flying karate kick in defense of a Dinamo supporter who was being truncheoned.
-- Josip Dasovic, Providence, R.I.

Brazil's Vasco da Gama and Flamango. It's the classic upper-class vs. lower-class showdown. When these team meet in the Maracana, they can only sell about half the seats because the divide between the two fan bases has to be that big.
-- Reed Larsen, Provo, Utah

MetroStars vs. D.C. United.
-- Tara, Basking Ridge, N.J.

Hmm. Not much of a rivalry, I'd say, considering the MetroStars' historical playoff success.

Lyon vs. St Etienne is certainly a bigger rivalry than Earthquakes-Galaxy. It's the bourgeoisie and silk city vs. the blue-collars and the coal mines. And if Lyon wins a fifth consecutive title, they'll break St Etienne's record of four. That only deserves an article in SI.com. Go Olympique Lyonnais.
-- Olivier, Lyon, France

Since you're talking internationals, how about England-Argentina? Nothing like the Falkland Islands to stir up some bad blood. For clubs, what about Manchester United-Arsenal? It's become a real grudge match over the past few years.
-- Omkar Muralidharan, Canton, Ohio

Boca Juniors vs. River Plate. Fanatic fans, rich vs. poor and what appears to be genuine hate combined with 100 years of history make it a classic.
-- Klavs, Copenhagen, Denmark

It is a little known fact that Canada-USA is the second-oldest rivalry in international football (after Scotland-England). While it may not be the passionate relationship that the likes of Argentina and England share, but it is cool to know there is a long history when the two countries meet.
-- Jonathan H., Vancouver, British Columbia

Canada plays soccer? (Sorry, cheap shot -- couldn't resist. Can I borrow some of your free health care?)

My favorite is the three-headed Ajax-Feyenoord-PSV Eindhoven hate-fest in the Dutch Eredivisie. One of the three has been champion, I think, all but one of the last 45 or 50 years. I have an Ajax-adoring friend from Amsterdam who never says the word "Feyenoord" -- he calls them kakkerlakken, which is Dutch for "cockroaches."
-- Brooke Saucier, Evanston, Ill.

Ouch. Any Legion fans gonna step up?

Manchester United vs. Arsenal The way these two teams have been going at it the last few years, anyone watching would be excused for thinking that the side that loses is going to be executed at the end.
-- Pratik Mitra, Warwick, England

Well said! Can't they agree to put aside their hatred and mutually rail against Chelsea?