Key stock benchmarks on Thursday decided to take a breather after three sessions of market frenzy. Both Sensex and Nifty settled with marginal gains in a session marked by sharp fluctuations. The BSE Sensex ended up 2.72 points, or 0.01 per cent, at 37,755, with 18 issues rising and 12 declining. NSE's Nifty settled slightly below the 11,350 mark at 11,343, up 1.55 points, or 0.01 per cent. In the 50-pack index, 27 stocks advanced, 21 declined and 2 remained unchanged.