To me it is god damn haven! 99 out of 100 matches in on that damn map...how bout you guys.
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Haven's the only well-designed competitive slayer map. The rest aren't very well thought-out. The only downside of Haven and Ragnarok is that they're chosen frequently. Know why? Because they're the only well-designed maps. Ragnarok because Bungie and Haven because Midship-similarity.