He was one of the earliest chess players to take the endgame into account when choosing and playing the opening. He was exceptionally talented in the endgame, particularly in rook endings, where he broke new ground in knowledge. Jeremy Silman ranked him as one of the five best endgame players of all time, and a master of rook endgames.
He originated the Rubinstein System against the Tarrasch Defense variation of the Queen's Gambit Declined: 1.d4 d5 2.Nf3 c5 3.c4 e6 4.cxd5 exd5 5.Nc3 Nc6 6.g3 Nf6 7.Bg2 cxd4 8.Nxd4 Qb6 (Rubinstein - Tarrasch, 1912). He is also credited with inventing the Meran Variation, which stems from the Queen's Gambit Declined but reaches a position of the Queen's Gambit Accepted, with Black one move ahead.
Today, he certainly has no shortage of lines named for him. The "Rubinstein Attack" often refers to 1 d4 d5 2 c4 e6 3 Nc3 Nf6 4 Bg5 Be7 5 e3 0-0 6 Nf3 Nbd7 7 Qc2. The Rubinstein Variation of the French Defence arises after 1 e4 e6 2 d4 d5 3 Nc3 (or 3 Nd2) dxe4 4 Nxe4. The Rubinstein Variation of the Nimzo-Indian is the most popular non-classical line of the Nimzo-Indian : 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.e3. Of course, there is also the Rubinstein Variation of the Four Knights Game which arises after 1 e4 e5 2 Nf3 Nc6 3 Nc3 Nf6 4 Bb5 Nd4, and the Rubinstein Variation of the Symmetrical English, 1. c4 c5 2. Nc3 Nf6 3. g3 d5 4. cxd5 Nxd5 5. Bg2 Nc7, a highly complex system which is very popular at the grandmaster level.
The Rubinstein Memorial tournament in his honor has been held annually since 1963 in Polanica Zdroj, with a glittering list of top-flight winners.