Heartless Hidetsugu in your deck rarely fails to make multiplayer games more interesting. Although he usually has a huge target on his head as soon as he hits play, if you activate him at least once, whether with haste or some sort of protection, you know the game is probably coming down to the wire in an intense wild west showdown. Now, maybe these moments are more fun for me but I think it is hard to deny the fact that this guy has an intensity that few other multiplayer cards have. It's by no means an immediate win card and is hard to do much with him without some support since he is so easy and desire to kill in addition to being generally unable to win the game on his own (damn you rounding down!), but, if your opponents answers have been exhausted or the right pieces of the puzzle fall together, winning with this guy is like being the good guy in a movie slowly walking away with a huge explosion behind you.
Although this card has a very experiential, splashy Timmy effect, this card is one of the most Johnny type cards I like to play with because it really needs to have support cards to make it work. As you all have witnessed, lifelink or haste are insane with this guy. Mother of Runes or some sort of protection is generally pretty essential too. Burn can be pretty essential too to finish off your opponents' last few life. I suppose it could be fun to throw this guy randomly into a multiplayer deck with little support, but by himself, while dealing a buttload of damage usually, Heartless Hidetsugu is a little too risky if you don't have a significant life advantage. Few other magic cards have such a powerful effect that speed up a multiplayer game but require such a maniacal master plan that takes into account all the ins and outs and counter-strategies. He is also my date to prom.