The Sensex opened with a positive gap of 43 points at 15,278, but slipped in early trades due to nervousness following the steep fall on Friday. The index tumbled to a low of 15,135 - down 143 points from the day's open.Aggressive buying in select stocks like Hindustan Unilever, SBI and cement shares helped the index rebound into positive zone. The buying momentum was so strong in mid-noon trades that the index rallied to a high of 15,452 - up 317 points from the day's low. Intra-day profit-taking saw the Sensex pare gains, and finally end with a marginal gain of 26 points at 15,261.The BSE Bankex rallied 1.7% to 8055, and the FMCG index was up nearly 1% at 1945. The Realty index dropped 2% to 7670, and the Metal index shed 1% at 11,381.The market breadth was slightly positive - out of 2,660 stocks traded, 1,342 advanced, 1,258 declined and 60 were unchanged today.INDEX MOVERS....Hindustan Unilever soared 6.3% to Rs 209 after the company announced a Rs 630 crore buy back plan at Rs 230 per share.SBI zoomed over 5% to Rs 1,579 on strong Q1 numbers.Ambuja Cements surged over 3% to Rs 129. Grasim advanced 3% to Rs 2,947, and ACC added 2% to Rs 1,023.Reliance Energy and Maruti rallied over 2% each to Rs 780 and Rs 847, respectively. Satyam moved up over 1% to Rs 479, and NTPC also gained over 1% at Rs 163.Tata Motors and ICICI Bank were up 1% each at Rs 707 and Rs 924, respectively.....AND THE SHAKERSHindalco plunged over 4% to Rs 166. Mahindra & Mahindra tumbled 3% to Rs 753.ITC shed 2.6% to Rs 167. TCS and Bajaj Auto slipped 1.3% each to Rs 1,138 and Rs 2,293, respectively.Dr.Reddy's, Reliance, BHEL and Infosys were down 1% each at Rs 636, Rs 1,848, Rs 1,644 and Rs 1,988, respectively.VALUE & VOLUME TOPPERSReliance topped the value chart with a turnover of Rs 217 crore followed by Reliance Energy (Rs 200 crore), HDIL (Rs 182.60 crore), SBI (Rs 178.20 crore) and Reliance Capital (Rs 153 crore).Reliance Natural Resources led the volume chart with trades of around 1.80 crore shares followed by Harig Cranks (1.15 crore), IKF Technologies (1.05 crore), IFCI (97.50 lakh) and Suryachakra Power (86.25 lakh).