It depends what you mean by exciting, but as far as last second plays, bragging rights, and ego, these two stand out:
=S3= vs NuTz, tiebreaker map for #1:
http://www.youtube.com/watch?v=GKeuHg1qb94
5150 vs Sticks, first map of 5150's last match, game is for #1:
http://www.youtube.com/watch?v=Nv7NSkDSdSc
I have a playlist of games that were decided by a point or two, some are better than others.
Close Games
n$ vs [KoV] on SH is worth a watch and so is UVA5 Team1 vs Team8 on DX.