Question: Which team, known along with Linfield as one of Belfast's "Big Two," did Walter McMillen play for?
Context: Walter S. McMillen (24 November 1913 – 11 May 1987) was a Northern Irish footballer.  His regular position was as a defender.  He was born in Belfast.  He played for Distillery, Manchester United, Cliftonville Strollers, Cliftonville Olympic, Chesterfield, Millwall, Glentoran and Linfield. Big two (also known as deuces and various other names), is a card game of Chinese origin.  It is similar to the games of president, crazy eights, cheat, winner, and other shedding games.  The game is very popular in East Asia and South East Asia, especially throughout China, Indonesia, Macau, Hong Kong, Malaysia and Singapore.  It is played both casually and as a gambling game.  It is usually played with two to four players, the entire deck being dealt out in either case (or sometimes with only 13 cards per player, if there are less than four players).  The objective of the game is to be the first to play of all of his cards.  It is sometimes confused with "tien len" (a.k.a. thirteen); the two games differ primarily in that big two involves poker hands, while "tien len" does not. Pusoy dos (or Filipino poker, also known as chikicha or sikitcha), a variation of big two, is a popular type of "shedding" card game with origins in the Philippines.  The object of the game is to be the first to discard one's hand by playing them to the table.  If one cannot be first to play all cards, then the aim is to have as few cards as possible.  Cards can be played separately or in certain combinations using poker hand rankings.  Games of Pusoy Dos can be played by three or four people. Sunnybank Football Club are a Scottish football club, based in the city of Aberdeen.  Members of the Scottish Junior Football Association, they currently play in the SJFA North First Division (East).  In respect of honours won, the club are historically regarded as one of the "big two" of North Region Junior football along with city rivals Banks O' Dee, sharing the distinction of being the only North clubs to lift Junior football's national prize, the Scottish Junior Cup.  The club are based at Heathryfold Park in the North-West suburbs of Aberdeen and their colours are black and white. Belfast's Big Two, also referred to simply as the Big Two, is the name given to the Northern Irish association football derby between Belfast clubs, Linfield and Glentoran.  The derby is also sometimes referred to as the Belfast derby.  They are the two most successful and most supported clubs in Northern Irish Football.  They traditionally face each other on Boxing Day each year which usually attracts the largest Irish Premiership attendance of the season.  They regularly play each other in the league and have contested more cup finals together than any other two clubs.  They also make up two of the three clubs that have appeared in every season of the Irish League since its inception in 1890 – the other club being Cliftonville. Cliftonville Football & Athletic Club (the Reds) is an Irish semi-professional association football club playing in the NIFL Irish Premiership.  The club was founded in September 1879 by John McCredy McAlery in the suburb of Cliftonville in north Belfast, it is the oldest football club in Ireland and celebrated its 130th anniversary in 2009.  Since 1890, the club has played at Solitude.  Cliftonville contests the North Belfast derby with nearest rivals Crusaders, and also has historical rivalries with Belfast's Big Two clubs, Glentoran and Linfield. Linfield Football Club is a semi-professional football club based in Belfast, Northern Ireland.  The club was founded in 1886 as Linfield Athletic Club and in 1905 moved into the current home of Windsor Park, which is also the home of the Northern Ireland national team.  The club plays in the NIFL Premiership – the highest level of the Northern Ireland Football League.  Linfield's main rival is Glentoran – the other half of Belfast's Big Two.  This rivalry traditionally includes a league derby played on Boxing Day each year, which usually attracts the largest league attendance of the season.  Linfield's average league home attendance is approximately 2,500 the highest in the division and more than double the league's overall average of about 1,000. Belfast Celtic Football Club was a football club in Northern Ireland that was founded in 1891, and was one of the most successful teams in Ireland until it withdrew from the Irish League in 1949.  It left the league for political reasons, as the team and its supporters were largely Catholic and Irish nationalist, and its players had been violently attacked by a mob against its main rival Linfield in December 1948.  Belfast Celtic were one of four clubs that made the biggest crowds in the Irish League, the other three being Linfield, Distillery, and Glentoran. Steven Bryce Valerio (born August 16, 1977) is a former Costa Rican footballer.  Bryce was well known along his career for his polyfunctuonality and his ability to play different roles at the field, such as: attacking midfileder, winger, striker and right back.  He is an attacking midfielder with good skills, pace, fast and strong. Glentoran Football Club is a semi-professional football club that plays in the NIFL Premiership.  The club was founded in 1882 and plays its home games at the Oval in east Belfast.  Club colours are red, green and black.  Linfield and Glentoran are nicknamed Belfast's "Big Two", as they have traditionally dominated local football in Northern Ireland since the demise of Belfast Celtic.  The two play a league match on Boxing Day each year, which regularly attracts the largest attendance of the Irish League season.
Answer: Glentoran Football Club