Editor's Note: In this feature from Stockpickr, we highlight lists of stocks that have made new highs, lows or seen other unusual activity.52-Week Highs: Credit card company MasterCard ( MA) hit a 52-week high for the second straight session, gaining another 4.3% after announcing on Friday its plans to convert Class B shares into Class A on an accelerated basis. The company gained $6.84 to $164.49. Biggest % Gainers: Harvest Natural Resources ( HNR) jumped 37% after Venezuela's National Assembly approved a change in operations under which the country would take a controlling stake. The stock gained $3.68 to $13.50. Rising on Unusual Volume: Diversified investments firm Life Partners ( LPHI) surged 7% Monday as shares traded at five times average volume. The Waco, Texas company added $2.07, closing at $32.18. 52-Week Lows: American Commercial Lines ( ACLI) fell down to a 52-week low Monday after the company lowered guidance. On the news, the shipping company's shares dropped $2.78, or 10%, to $24.35. Biggest % Losers: Encysive ( ENCY) plummeted 44% Monday after the Food and Drug Administration rejected the company's pulmonary arterial hypertension treatment, Thelin. Shares fell $1.78, landing at $2.32. Stocks with Unusual Option Activity: Orbcomm ( ORBC) was experiencing unusual option activity on Monday. Shares lost 11 cents, or 0.7%, to close at $16.09. Latest Activist Situations: Two hedge fund heavyweights, SAC Capital and Citadel, bought up shares of biotech company BioMarin Pharmaceutical ( BMRN). Monday, SAC Capital disclosed it owns a 5.1% "passive" stake in the company, and Citadel disclosed a 5.5% "passive" stake in the company. The company's shares gained 23 cents, or 1.3%, closing at $18.01.