The most often played opening move at the Gibraltar Open was 1.e4 (45%). Of course, in many of these games, Black replied with 1...e5. However, the really "hot" variations were seen in the semi-open games. Here are the current trends:
As far as I can see the Caro-Kann was the most often theoretically debated opening (53 games). This opening is not only solid but its modern interpretation even offers Black good winning chances. In Gibraltar, the German players Rasmus Svane and Dennes Abel were particularly avid Caro-Kann followers.

Nakamura-Svane | Photo: John Saunders
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Remarkable was the fashionable "...f7-f6" which came as a novelty in several games from Gibraltar. In the old main line Vidit's recommendation is still a good option although it did not really work in the Saric game above.
But the most popular reply (197 games) to 1.e4 is still the Sicilian (1...c5). Professionals like to play the Open Sicilian but among amateurs, sidelines are popular. Some players tried Nge2 to hinder Black from reaching his favourite set-ups or to get an improved Grand Prix Attack (as in the Gary Quillan game below). The Rossolimo is also a popular line against the Sicilian. Here, the game Navara-Grandelius was particularly interesting.
David Navara on his win over Grandelius
The Najdorf appeared in 31 games and to counter it White tried no less than eleven alternatives on move six. However, only three players were confident enough to play 6.Bg5, formerly the main move. Playing 6.Bg5 — and playing against it — requires a lot of theoretical work but still leads to interesting games. (See Sosa 0-1 Moussard below.)
The Dragon was played in three games, the Sveshnikov in nine, and in these nine games White scored a bit better (+3 -2 =4). Caruana's 7.Nd5 from the World Championship match against Carlsen was only tried by Wesley So who won a convincing game with it. In the other eight games, White played 7.Bg5.
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Wesley So follows Caruana's World Championship theory
Sicilians with 2...e6 were also popular in Gibraltar and in twelve games the Paulsen appeared on the board (as in the Melkumyan vs Bilguun above). In these games Black most often tried to reach a Hedgehog structure, occasionally giving up the bishop on c3.
The game that won the brilliancy prize in Gibraltar ended in a draw. Gawain Jones played with White against Alejandro Ramirez. But in general, the French did not fare particularly well in Gibraltar.

Alejandro Ramirez and Gawain Jones receive their joint Best Game prize from Hon. Steven Linares, MP, Minister for Culture, Media, Youth and Sport | Photo: Niki Riga