Twinblade Paladin 
Creature — Human Knight
Whenever you gain life, put a +1/+1 counter on this creature. As long as you have 25 or more life, this creature has double strike. (It deals both first-strike and regular combat damage.)
Legality
standardLEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL