Show your 8-bit love this Valentine's day by printing and wiring up your own "8-bit Heart".
I picked my resistors using this resistor calc:
I then divided the result by three for a few reasons: Firstly the LEDs I'm using (like my dearest) are cheap and dim. Secondly each LED will only be briefly lit for less than 1/3 of the time, and finally (like my love) nothing lasts forever.
First we will need to decide on which setup we'll be doing. The options are for a single heart, two or four. In this example I'll be doing the single (If you really loved them you'd do 2 or 4, but I'm like "meh, good enough"), but it's simple enough to extrapolate the 2 and 4 heart versions by multiplying the led count by 2 or 4 and adjusting the resistors (actually I suspect wiring all four may require more power than the Arduino can supply, but I'll update when I know for sure).
Edit: Woops... I seem to have forgotten the STL and thingiverse links (bonus .scad for the real 3d geeks).