We had a good Dragon Slayer group, with people being the best at their role while mixing in some feats and prestige classes from the Draconomicon. The whole line-up was about having a few strong fighters geared to fight dragons and a support team to help them out.
We were working our way up in levels, but some changes to the group outside of the game made it hard to continue, and the best dragon-slayer we had was killed by a scorpian. Ugh.
There was a nice combo going with a Dragon Slayer who had two previous levels of Wizard, so for first level of Slayer could take the Wraithstrike spell. You could cast that as a swift action and then charge. 6th level feat Favored Power Attack (1 level of Ranger) and 9th level feat Leap Attack. Use a two-handed weapon and you can do insane damage.
The druid could Snake's Swiftness, and the Mage could benign transpose him with the heavily armored cleric so he could charge again the second round. On the first round we had one character that would lead the charge...their entire purpose was to be a decoy, drawing AoO before the two real fighters charged in.