To do little or no damage try some penetrating oil (not WD40 since it's not a lube), wait several minutes, and try using strap wrenchs. You can find strap wrenches at Harbor Freight and other places for very little money.
If it's still not moving, apply a bit more oil and tap the end gently. Wait a few more minutes and give it another try.
Let us know if that doesn't work and someone will give another suggestion.