Williams Companies (WMB) had the best day in 2015 by a US stock with a market cap of $50B+ on June 22, 2015, returning 25.9%.

ASSET	DATE	% RETURN
Williams Companies (WMB)	6/22/2015	25.9%
Shopify (SHOP)	9/17/2015	18.94%
Freeport-McMoran Copper & Gold (FCX)	8/27/2015	18.08%
Freeport-McMoran Copper & Gold (FCX)	8/10/2015	15.23%
Advanced Micro Devices (AMD)	2/5/2015	14.93%
Advanced Micro Devices (AMD)	8/3/2015	13.99%
MPLX (MPLX)	12/8/2015	13.73%
Energy Transfer (ET)	12/23/2015	13.58%
Petróleo Brasileiro SA - Petrobras (PBR.A)	10/2/2015	13.54%
Cadence Design Systems (CDNS)	12/1/2015	13.28%
Alibaba (BABA)	8/24/2015	13.14%
Cigna (CI)	6/15/2015	12.73%
Salesforce (CRM)	4/29/2015	12.58%
ONEOK (OKE)	12/21/2015	12.57%
Advanced Micro Devices (AMD)	1/21/2015	12.39%
Petroleo Brasileiro Petrobras SA ADR (PBR)	10/2/2015	12.08%
MPLX (MPLX)	12/9/2015	11.81%
Energy Transfer (ET)	12/9/2015	11.78%
Norfolk Southern (NSC)	11/9/2015	11.26%
Freeport-McMoran Copper & Gold (FCX)	12/23/2015	11.19%
Zoetis (ZTS)	6/25/2015	11.12%
Petroleo Brasileiro Petrobras SA ADR (PBR)	4/23/2015	11.11%
Advanced Micro Devices (AMD)	7/29/2015	10.73%
Enterprise Products Partners (EPD)	9/30/2015	10.47%
Williams Companies (WMB)	12/23/2015	10.08%