Well done Arnie! You've done us proud. Smoke me a kipper, I'll be back for...
~ Ace's last words before his death.
Ace Rimmer is the alternate reality version of Arnold Judas Rimmer however unlike the "real" Rimmer Ace is a very heroic, selfless, brave and charming man who saves princesses, overthrows dictatorships, etc.
He was portrayed by Chris Barrie.
What a guy!
~ What various characters say about Ace.
Ace is the exact opposite of Rimmer with every personality trait contrasting one of Rimmer's this is due to him repeating a year in school while his alternate reality counterpart continued on into the next year leading to the two becoming exact opposites. Rimmer himself can't stand Ace, always calling him a "smug git" while everyone else adores him, annoying Rimmer even further. Ace despite Rimmer clearly despising him Ace always does try to be civil and friendly with him showing that he is indeed a much better person. In "Stoke Me A Clipper" it is revealed that Ace Rimmer is actually a title passed on to various Arnold Rimmer after the current Ace has died. The current Ace after being mortally wounded by a bullet goes into the main series Rimmer's dimension to train him into becoming Ace, revealing that he's not even a human or the Ace that crew originally met, saying that he's a hard light hologram who took over from the previous one. Rimmer is reluctant at first but eventually agrees, shortly before his death the current Ace uses a light-bee remote to change his clothing into that of Ace's. He then lays on the bed awaiting his death while Rimmer gets into a battle with one of the VR knights who is hunting Lister (who was actually just Lister himself in disguise). After Rimmer kills the knight (stuns Lister in disguise), he runs back to Ace telling him what he did. Ace says he's proud of him before dying. Rimmer sits at the end of the bed in shock while the rest of the crew come in, Lister then makes the cover story saying that one of the knights broke out of the VR machine and killed Rimmer whilst looking for Lister himself. Rimmer and Lister then talk about what Rimmer should do, leading to Lister telling him about the coffin for Ace's light-bee and how after the funeral they should follow it for Rimmer to make his final decision. Rimmer then decides to embrace his future and becomes Ace, giving one more final goodbye to his old crew. The original Rimmer has so far never returned but it is possible he could come back in a later season.
Ace's character was actually created by Chris Barrie due to him wanting to play a heroic character (not counting the original Rimmer who is an anti-villain.
Ace's original wig was stolen from set and had to be replaced with an inferior one in his subsequent appearances.