Toothache said:
Houndoom is my kinda Pokemon, so you gotta get it right...
Houndoom@Lum Berry/no item
EV: 252 Speed, 252 Sp Att, 6 Sp Def
Nature: + Speed, - Att
Crunch/Pursuit
Sunny Day/Torment/Thief/Snatch
Solarbeam/HP Special
Flamethrower/Fire Blast
Wish works well with the Sunnybeamer strategy against Water types (but Swift Swimmers make short work of Houndoom). Since Houndoom is a 'kill or be killed' type of Pokemon, consider Thief to steal a tank's Leftovers before death. Torment can give a slight edge, as a pseudohaze or for protection. Use Snatch if you're expecting Dragon Dance or another stat boost (but watch out for Tauntrados)
As for the Counter/Rest tactic, you'd need max Defence and HP to even attempt this, and you have to expect anything that's not super-effective. Houndoom can't withstand a super-effective physical move even at full defence, so I wouldn't recommend this strategy.
My general rule about EVs in defense is...
HP EVs are more important than the other two EVs. Why is this? Because HP is the general defense. Whenever a Pokemon takes damage, be it from Special or Physical, it always gets taken out from the HPs. Putting EVs into only Special Attack helps out against moves in ONLY the Special range. Same with EVs in Defense. EVs in HP are more important than EVs in the two other defenses. If you want a tank, then max out HP and then split the EVs between the other two defenses or whatnot. But HP>Def and SDef.
In any case, Fire Blast>Flamethrower, since as you even stated, he's a "kill or be killed" monster. Fire Blast is the best move of all 120 Attack Power attacks. Hydro Pump has lower accuracy and no side effect. Solar Beam takes two turns. Thunder has lower accuracy. Blizzard has lower accuracy. Fire Blast has 85% Accuracy and 10% chance to Burn. So since Houndoom is a "Kill or be killed" monster, lets go with Fire Blast.
He doesn't have the defenses for Torment. As much as it is a good idea, he won't last long to begin with.
Snatching Dragon Dance is only good for the Speed Boost. But never leave Houndoom against a Dragon Dancer anyway, because Houndoom will get raped =[
Pursuit is good against those fugly Psychic types (Hypno, Alakazam, Gardevoir, Eggy). And it is a good move to have in a Spikes team, because if they switch, they get double the damage as they leave then get damage when they come in. I made a Spikes team once with a couple Pokemon that had Pursuit, and boy did it work well. Crunch is just an all around great move (HIE Special Defense drop). Pursuit takes a little more skill to use, and since I'm lazy most of the time, I stick with Crunch.
Sunny Day and Solarbeam are the other two moves I'd suggest anyway. GFG Golem/Rhydon =[