Yes, Fire/Grass
Reasons for Fire/Grass:
Complimentarity:
Fire, for all the hate it gets, has 5 resistances, 3 of which nuetralize Grass's long list of weaknesses.
Similarly, of Grass's 4 resistances, 2 of those neutralize Fire's weaknesses.
The net result:
Resist: Grass 4x, Electric 2x, Steel 2x
Weak: Rock 2x, Poison 2x, Flying 2x
Rock is the only really common weakness here. Most of the Poisons really don't take a decently powered Fire Blast well, and the most common deleiverer of fling attacks, Skarmory, doesn't want to set foot anywhere near Fire Blast. Togekiss is the biggest problem, really.
Fire type that doesn't imediately die when Gyarados switches in? Quite GG. Sure, there might be a few Stone Edge variants around, but Waterfall/EQ/Ice Fang will be SOL while it eats 120 BP STAB Grass Knots.
Grass type that doesn't wilt every time Weavile or random IBeam packing water switches in (or happens to be out)? yes plox. For all the weirdness it seems, Fire nuetralizes the biggest water-type counter to Grass types since it now takes nuetral damage from Ice Beam.
STAB Combo Fire/Grass has a lot of good coverage, and is resisted only by Dragons and oher Fire types. Thing is, only the Dragon/Flying types actually still resist both, and they can be addressed by HP Ice. Heatran is probably the biggest problem for the combo. However, Fire types pretty much immediately lose their efficacy as counters if we give this Flash Fire, bar Moltres who could use a Flying move.
Not only that, but they cover the traditional weaknesses of either type. Grass hits Water, Rock, and Ground types hard, while Fire demolishes the Bug, Ice, and Steel types that give grassers headaches, while taking out other Grassers that just stall them out.
Not only that, but Fire Blast is pretty much pound-for-pound the best 120 BP special move. On a Sunnybeam set it would have a fairly accurate and ridiculously powerful FB combined with a STAB 100% acc Solarbeam.
Support:
Leech Seed is awesome. Will-O-Wisp is awesome. Leech Seed and WoW is wtf mate! If it gets Lava Plume than even better. Grassers also traditionnally have Powders, although that might make less sense on a part fire type. Still, Leech Seed, Sleep Powder, Stun Spore, and Will-O-Wisp would be BEAST (not all in the same set).