 If you liked
Gyakkyou Burai Kaiji: Ultimate Survivor
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 ...then you might like
Steins;Gate
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Both animes have a great amount of psychological thriller, both keep you guessing, both have intellectual methods to counter problems.
If you enjoyed Steins Gate intense twists and suspense, then I assure you Kaiji delievers a lot better.
However if you would like to add some comedy + romance in, Steins Gate is the one.