If I'm down to three or four players (final table) and I'm first to act pre-flop, I'll just call with them. But be careful with that though: the big blind might check and hit three of a kind off the flop or decides to chase a flush or open-ended straight. If I'm on the button there, I'll play it more aggressively.
If it's just in the beginning (and, again, first to act pre-flop), I'll play them very aggressively, just because I don't want anyone to get lucky and/or chase. Brunson describes it differently in the Super/System, but that's just me. I've been burned playing pocket aces or kings by experimenting. I prefer to just take down the pot, no matter how small it may be in the early stages of a tournie.
But if I get them on the button in any stage of a tournie, I'll play them aggressively regardless.