For a list of active players with 10 or more threes in a game see here. To date, no player has ever made 10 or more threes in a playoff game. Four players have made nine threes in playoff games a total of five times.
All the NBA players who made ten or more threes in a game
T-1. Kobe Bryant - 12
Kobe Bryant set the NBA record for most threes in a game with 12 on January 7, 2003, in a game vs the Seattle SuperSonics (now Oklahoma City Thunder). Kobe made 12 of the 18 threes he attempted in the game. He also scored 45 points, as the Lakers beat Seattle, 119-98.
T-1. Donyell Marshall - 12
Donyell Marshall tied Kobe Bryant's record when he made 12 threes in a game for the Toronto Raptors playing against the Philadelphia 76ers on March 13, 2005. Marshall came of the bench to make 12 of the 19 threes he took in the game. He scored 38 points, as the Raptors beat the 76ers, 128-100.
T-3. Deron Williams - 11
Deron Williams of the Brooklyn Nets made 11 threes in a game vs the Washington Wizards on March 8, 2013. Williams made 11 of the 16 threes he took in the game, including an NBA record nine threes in the first half. That's the most threes ever made in a NBA game in one half by a player.
For the game, Deron Williams scored 42 points, as the Nets beat the Wizards, 95-78.
T-3. Stephen Curry - 11
Stephen Curry of the Golden State Warriors made 11 threes in a game vs the New York Knicks on February 27, 2013. Steph Curry made 11 of the 13 threes he took, as he scored a career high 54 points in the game. The Knicks beat the Warriors, though, 109-105.
The 54 points by Stephen Curry, also known as Steph Curry, are the most by any player on this list for the game in which they made 10 or more threes.
T-3. J.R. Smith - 11
J.R. Smith of the Denver Nuggets made 11 threes in a game vs the Sacramento Kings on April 13, 2009. Smith came off the bench to make 11 of the 18 threes he took, as he scored 45 points to lead the Nuggets to a 118-98 win.
T-3. Dennis Scott - 11
When he made 11 threes in a game for the Orlando Magic vs the Atlanta Hawks on April 18, 1996, Dennis Scott established the NBA record for most threes in a game that Kobe Bryant broke in 2003. Scott made 11 of the 17 threes he took, and scored 35 points in the game, as he led Orlando to a 119-104 win.
T-7. Mario Chalmers (Miami Heat) - 10 (1-12-2013, made 10 of 13 threes, scored 34 points)
T-7. Ty Lawson (Nuggets) - 10 (4-9-2011, made 10 of 11 threes, scored 37 points)
T-7. J.R. Smith (Nuggets) - 10 (12-23-2009, made 10 of 17 threes, scored 41 points)
Only player with two 10 or more three-point games in NBA history.
T-7. Peja Stojakovic (New Orleans Hornets) - 10 (6-11-2007, made 10 of 13 threes, scored 36 points)
T-7. Ray Allen (Milwaukee Bucks) - 10 (4-14-2002, made 10 of 14 threes, scored 47 points)
T-7. George McCloud (Dallas Mavericks) - 10 (12-16-1995, made 10 of 12 threes, scored 36 points)
T-7. Joe Dumars (Detroit Pistons) - 10 (8-11-1994, made 10 of 18 threes, scored 40 points)
T-7. Brian Shaw (Miami Heat) - 10 (4-8-1993, made 10 of 15 threes, scored 32 points)
Shaw set the NBA record for threes in a game which Dennis Scott broke in 1995.