Akers made four field goals to give him 42 this season, most in league history, and San Francisco eliminated Seattle from postseason contention by holding off the Seahawks 19-17 on Saturday.
The NFC West champions remained in position for the No. 2 playoff seed and a first-round bye thanks to Akers and an impressive second-half effort on defense.
"I thought it was, like I said, a real good preview for what the playoffs are going to be like," 49ers coach Jim Harbaugh said. "Overcoming adversity. Nobody flinched. We had some real difficult situations, you know, some real pressure-to-perform situations, and our guys performed."
With the Seahawks fighting to stay alive in the playoff race, San Francisco had to rally multiple times. The 49ers overcame a 17-16 deficit after Marshawn Lynch scored on a 4-yard TD run with 6:41 left and was showered with candy.
The 49ers were in such a good mood that San Francisco coaches ran through the press box in the closing seconds shouting "Merry Christmas everybody," as Smith took a knee to drain the final seconds.
Akers' 39-yard field goal with 2:57 left proved to be the game-winner -- but it was Grant who was the game-clincher. As the Seahawks (7-8) tried to drive for the winning score, Grant's tackle of quarterback Tarvaris Jackson from behind jarred the ball loose and it was recovered by Donte Whitner at the San Francisco 36 with 1:07 remaining.
Filling in for injured Patrick Willis, the standout linebacker who missed his third straight game with a hamstring injury, Grant missed Jackson on his initial blitz, only to come from behind and strip the QB for the only turnover of the game.
If Grant had not forced the fumble, Jackson likely would have gained enough to convert the third down and keep the Seahawks' drive going.
"He doesn't tuck it at all, he keeps it loose and keeps his eyes downfield," Grant said. "Knowing he does that, when you're coming from behind the first thought is you've got to rake for the ball."
San Francisco limited the Seahawks to 72 total yards in the second half and Seattle's only points came following a blocked punt.
The 49ers could head into next week's regular-season finale at St. Louis with the No. 2 seed locked up if Atlanta wins at New Orleans on Monday night. They still have a shot at the No. 1 seed, but would need Green Bay to lose its final two games.
Regardless, all San Francisco needs is a win over the lowly Rams to clinch a home playoff game and a weekend of rest that could be critical. The 49ers played without Willis and wide receiver Ted Ginn Jr., then saw tight end Delanie Walker and receiver Kyle Williams go down with injuries.
Early in the fourth quarter, Akers connected from 44 yards out for his 41st field goal of the season, breaking the NFL mark set by Neil Rackers in 2005 with Arizona.
Akers also hit from 53 and 29 yards. He missed a 52-yard attempt in the first quarter and is 42 for 49 this season.
"All our players and coaches, everybody is really happy for David's success," Harbaugh said. "Another great effort by him today."
Smith protected the ball, as he has all season, and his biggest throw set up Akers' decisive kick. On second-and-18 from his own 31 with 5:51 left, Smith threw deep for Crabtree, who got just enough separation from Brandon Browner to haul in the 41-yard reception. The 49ers didn't advance any further, but were in range for Akers to give them the lead.
Smith finished 14 of 26 for 179 yards, while Crabtree had five catches for 85 yards. The bigger contributions came from Frank Gore and his backup, Kendall Hunter. Gore scored on a 4-yard run on the first drive of the second half and finished with 83 yards rushing, while Hunter added 73 on just 12 carries.
If there was a disappointment for San Francisco it was seeing its streak of not allowing a touchdown rushing or a 100-yard rusher end. Lynch finished with 107 yards on 21 carries, the first back to top 100 yards against the 49ers since Green Bay's Ryan Grant in Week 11 of the 2009 season. Lynch's touchdown run in the fourth quarter was the first allowed by San Francisco all season.
"If Marshawn Lynch isn't in the Pro Bowl, there is something wrong with the voting system," said Seattle wide receiver Doug Baldwin, who caught a 13-yard TD pass in the first quarter. "Plain and simple, he's proved it week in and week out."
San Francisco's defense was so strong in the second half that it took a special teams mistake for Seattle to have a chance. Heath Farwell blocked Andy Lee's punt to set up Lynch's TD, his 11th straight game with a score. It set off a shower of Skittles flying out of the stands. The candy covered the blue-painted end zone to the point where workers with industrial blowers came out to try and clear the field.
But the 49ers responded with Smith's throw to Crabtree and later with Grant making the play they needed as the San Francisco sideline burst into celebration.
"Our guys came back and answered," Harbaugh said.
Walker was taken to a hospital to be examined after getting kneed in the jaw inadvertently by Seattle LB Leroy Hill. A team source told ESPN NFL Insider Adam Schefter that Walker broke his jaw in the collision. Walker was expected to fly back to San Francisco with the team. ... San Francisco won in Seattle for the first time since 2008. ... Seattle finished the season 4-4 at home. ... Akers' previous career high for FGs was 33 in 2008.
Information from The Associated Press contributed to this report.