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: Priceline.com ( PCLN) vaulted 22% Wednesday after the online travel company posted second-quarter earnings that shattered expectations. The company posted adjusted earnings of $47.3 million, or $1.11 a share, on revenue of $355.9 million. Analysts expected earnings of 89 cents a share on revenue of $354.3 million. The stock jumped $14.47 to a 52-week high at $79.56. Rising on Unusual Volume: Priceline.com's ascent was on the back of volume more than seven times its three-month average. Biggest % Gainers: Impac Mortgage Holdings ( IMH) surged 47% after reassuring investors it has enough capital to satisfy future margin calls. The stock had plummeted Tuesday, after a UBS analyst expressed doubt regarding whether Impac can meet margin calls. Wednesday the company made up for some lost ground, adding 57 cents at $1.79. Biggest % Losers: Heelys ( HLYS) plunged 48% after the maker of wheeled sneakers posted impressive second-quarter results but said third-quarter results would be disappointing. The company earned $12.8 million, or 45 cents a share, on revenue of $74.3 million. Looking ahead, Heelys sees third-quarter earnings of 28 cents to 30 cents a share on revenue of $55 million to $58 million. Shares closed down $10.57 to $11.42. 52-Week Lows: Heelys sunk to a 52-week low. Stocks with Unusual Option Activity: Medarex ( MEDX) was experiencing unusual option activity Wednesday. The biopharmaceutical company closed up $1.40, or 8.9%, to $17.01. Latest Activist Situations: In a filing with the Securities and Exchange Commission, HealthCor Management disclosed a 9.01% stake in Trimeris ( TRMS) and noted it is interested in having discussions with the company's management concerning various strategies for maximizing shareholder value. The firm said they have requested a meeting with the company's management. The company closed up 63 cents Wednesday, or 10.8%, to $6.42.