Dragonborn Water Orc is always bandied about as a good combat race (Water Orc is from Unearthed Arcana and can also be found in the SRD). +4 Str/Con, -2 to everything else. As orcs, they also qualify for Heedless Charge, which doubles damage on a charge at the cost of provoking an AoO from your target. If you're a mounted charger with a lance, your reach means you're less likely to be at risk of provoking that AoO at all (if your opponent can't reach you back), and it's more charging goodness.
Small characters may have a harder time going for the walking BFC route. It's harder for them to get long reach to control a large area (since it's easiest to get it from size), and their ability to trip (one of the main methods of stopping enemy movement) is dramatically impaired (lower Str, -4 size penalty, and you flat-out can't trip anything more than 1 size larger than you).
Under ability scores, Constitution says "Make this your secondary stat, after either Strength or Constitution."
War Mind is a good option for Knights (if you can get the Know(psionics) ranks). 5 levels and the Practiced Manifester feat gives you Sweeping Strike (attack two enemies for the price of one), the Expansion power (with the ML and PP to augment it to +2 sizes and long-term duration), +2 to Str/Con 3/day, +2 AC 3/day, DR 1/-, and a 2nd level power. I'd strongly consider taking the 6th level, too, for a 3rd level power and an extra +1 to all saves, if you don't have anything better to take. The 2nd-level power can even be Prowess (extra AoO as an immediate action), letting you spare some points of Dex to use for Wis to manifest it all.