If you're liking creature decks, you definitely want to check out slivers. They're particularly cool because each sliver (almost anyway) has an effect that affects all other slivers. For example, a muscle sliver will give all other slivers +1/+1 passively, which means having four of them out would allow all your slivers to collectively get +4/+4, which is huge. There are other effects like giving trample and first strike and many more - it's a really interesting deck to play as and against.
I never did the whole tournament thing aside from a few Friday Night Magic evenings at the local comic shop, so I guess I'm not quite as knowledgeable as you. I always found sliver decks to be particularly powerful and cool, though I guess there are decks that would probably outpace them pretty handily.
I don't recall, but aren't there some slivers that can mana fix? I've tried running a green/white elf deck before. Oh man, it's so fun to play because elves get so ridiculous after you get a Llanowar Elf or two out. It just ramps up so quickly.
Man, I miss playing Magic. I recall poring over cards and spending hour after hour thinking up novel combos to play against our friends. I mean, we played super casually, in that we didn't have any block restrictions or anything like that... but we followed the rules to a T.
