Ozil, 24, signed a long-term contract at the Emirates Stadium for a fee reported to be in excess of £40million, giving the club's fans the big-name signing they craved.
The attacking midfielder joined Arsene Wenger's side in the last hour before the transfer window shut, and his arrival is a significant boost to the club's hopes this season.
Monday's other biggest deal saw Manchester United finally complete the signing of midfielder Marouane Fellaini from Everton for a fee of £27.5million.
The 25-year-old became David Moyes' second signing following the arrival of young full-back Guillermo Varela, though the Scot allowed Bebe to leave for Pacos de Ferreira.
Sakho, 23, arrived from Paris Saint-Germain for a reported fee in the region of £18million and the Frenchman will give manager Brendan Rodgers options in central defence, while another player in that position, Tiago Ilori, joined from Sporting Lisbon.
Mariappa, a centre-back from Reading, and left-back Hunt – who joined from Huddersfield Town – will give Palace depth, while Scotland international Bannan was brought in from Aston Villa.
Stoke City completed the first move of Monday, with striker Marko Arnautovic signing from Werder Bremen on a four-year deal, while Aston Villa's Stephen Ireland joined on loan for the season.
Despite further bolstering their squad with the acquisition of Victor Anichebe from Everton, there was late disappointment for Steve Clarke's side as they missed out to the same club on the loan signature of Romelu Lukaku from Chelsea.
Armed with the money from Fellaini's sale, Roberto Martinez's side went on to add James McCarthy to their ranks on a permanent basis, while Gareth Barry and Romelu Lukaku arrived on temporary deals from Manchester City and Chelsea.
Elsewhere, Aston Villa signed Czech striker Libor Kozak from Lazio, for a fee reportedly worth £7million, Swansea loaned Alvaro Vazquez from Getafe and Manchester United defender Nick Powell joined Championship side Wigan Athletic, also on loan for the duration of the season.
Stoke sent Ryan Shotton out to Wigan for the season, as Tottenham also allowed Tom Carroll and Benoit Assou-Ekotto to drop down to the Championship with QPR and Fulham signed Elsad Zverotic from Young Boys.
