Celsius (CELH) had the best month in 2014 by a large-cap US stock in March 2014, returning 97.7%.

ASSET	MONTH	% RETURN
Celsius (CELH)	March 2014	97.7%
Neurocrine Biosciences (NBIX)	January 2014	84.36%
QXO (QXO)	November 2014	70%
Insmed (INSM)	June 2014	52.17%
TKO (TKO)	January 2014	46.16%
Monster Beverage (MNST)	August 2014	37.6%
Illumina (ILMN)	January 2014	37.58%
Trip Group Ltd ADR (TCOM)	February 2014	36.73%
Incyte (INCY)	October 2014	36.47%
IAMGold (IAG)	June 2014	36.42%
Coeur Mining (CDE)	June 2014	35%
Texas Pacific Land Trust (TPL)	February 2014	34.87%
Tesla (TSLA)	February 2014	33.86%
American Airlines (AAL)	January 2014	33.83%
EXACT Sciences (EXAS)	August 2014	33.83%
Centrais Elétricas Brasileiras SA - Eletrobrás (AXIA)	August 2014	32.49%
Centrais Electricas Brasileiras (EBR)	August 2014	32.49%
Centrais Elétricas Brasileiras SA - Eletrobrás (AXIA)	March 2014	32.1%
Centrais Electricas Brasileiras (EBR)	March 2014	32.09%
Sibanye Gold Ltd ADR (SBSW)	February 2014	31.96%
Lattice Semiconductor (LSCC)	February 2014	31.88%
Tower Semiconductor (TSEM)	November 2014	31.36%
Vertex Pharmaceuticals (VRTX)	June 2014	31.21%
EPAM Systems (EPAM)	May 2014	30.57%
Axon Enterprise (AXON)	August 2014	30.47%

Large-cap stocks are treated as having a market cap of $10B+.