Our LGS runs pretty much only Standard and limited events. The community has been pushing for more variety (I've pushed for Legacy, but to no avail) so the owner finally decided to run a Modern event. He recently had someone offload a collection so 1st prize was a Tarmagoyf. Had this taken place during the Modern PTQ season I think the turnout would have been a lot better. However, there were only twelve players, although the calibre was pretty high as several of the players had top 8'd PTQs in the past, played at Nats, etc.

With no Modern deck to speak of, I went to my existing decks to see what I could port over easily. The one that was the easiest was my Legacy Tezz-Affinity deck, having only to swap out my artifact lands and Ancient Tombs for inferior lands. So this is the list I ended up running

//Land
4 Darksteel Citadel
4 Inkmoth Nexus
4 Island
3 Swamp

//Creatures
4 Memnite
4 Ornithopter
4 Signal Pest
4 Frogmite
4 Myr Enforcer
4 Etched Champion
4 Master of Etherium

//Spells
3 Mox Opal
4 Springleaf Drum
4 Cranial Plating
3 Tezzeret, Agent of Bolas
4 Thoughtcast

//Sideboard
2 Arcbound Ravager
2 Despise
2 Pithing Needle
2 Relic of Progenetis
2 Hex Parasite
3 Ethersworn Cannonist
2 Dispatch

I realize you're looking at my sideboard and going "WTF?!". Yeah, it's pretty bad, thrown together without much thought. I was expecting to see Pod and Tron, but probably should have thrown in some Disenchants.

Round 1 - Alex Gabriel (RUW Delver)
I sat down across from Alex and said "Well, guess I'm opening the tournament at 0-1". Alex is a really nice guy, and one of the better players at the store.
Game 1 - Alex does himself a lot of damage with fetches and shock lands, making my life a little easier. I drop a Master and a couple of Etched Champions and come race his flipped Delvers
Game 2 - I didn't sideboard anything in. Again, Alex takes most of his damage from his lands. My notes are sketchy but memory seems to indicate that the managed to Disenchant and Helix my good stuff and flew in with flipped Delvers for the win.
Game 3 - Alex recovers from shock/fetch damage with a couple of Helixes, but a resolved Tezzeret allows me to search up answers and deflect damage away from me and towards Tezz. Etched Champions FTW!
1-0 (2-1)

Round 2 - Brandon Vasko (BW Tokens)
Brandon is a regular at the store, fairly good but we seem to have a good split against each other
Game 1 - I mull to six, but a turn one Soul Warden doesn't bode well for me. Midnight Hauntings, Lingering Souls, Raise the Alarm, and it's game over for me
SB - +2 Despise, +2 Dispatch, -4 Myr Enforcer
Game 2 - The swarm comes out, as I manage to swing in for 7, then lethal the next turn
Game 3 - Again, mull to six A Soul Warden, a bunch of tokens, and an Intangible Virtue make semi-quick work of me
1-1 (3-3)

Round 3 - Blake Alty (Aggro-Loam)
Another regular who I routinely split my matches with. I know he's on Aggro-Loam as I've seen him building and testing it over a number of weeks
Game 1 - Shock/Fetch does a bit of work. Etched Champion and Cranial Plating go the distance.
SB - +2 Pithing Needle, +2 Relic of Progenetis, -4 Myr Enforcer
Game 2 - As typical in most matches, Etched Champion does most of the heavy lifting, with support from his friends and Cranial Plating.
2-1 (5-3)

Round 4 - Jeff Mcarthy (UW Affinity)
This is win and in. Never seen Jeff at the store before, which is good because I like to see our community grow even more.
Game 1 - We start throwing our hands on the table and racing. His racing is better than mine, with a Tempered Steel and Steel Overseer overwhelming my Champion-less board
SB - +2 Dispatch, +2 Despise, +2 Pithing Needle, -4 Myr Enforcer, -2 Frogmite
Game 2 - I Dispatch his Overseer early, and I Poison him out for the win with a Cranial Plated Inkmoth.
Game 3 - My notes are non-existent here, but if memory serves me correct, he was getting artifact screwed here. He had to trade his Memnites and Ornithopters for my creatures, so could never get Metalcraft online. Eventually he just caved and I was on my way to top 4
3-1 (7-4)

I placed 4th after swiss, so I played 1st place. Other match was Twin vs BW tokens

Semis - Jamie Hennessey (Jund)
I've seen Jamie a few times, never played him. Again, one of the better players around, hangs out with Alex (from round 1) and Mike (from the next round).
Game 1 - A couple of Etched Champions make it around his Tarmagoyf. The Etched Champions really give him a hard time as he has no way to deal with them. Shock/Fetch does the up front work for me and the Champions do the rest of the work
SB - +2 Relic of Progenetis, +2 Dispatch, +3 Ethersworn Cannonist, -4 Myr Enforcer, -2 Signal Pest, -1 Frogmite
Game 1 - Puke most of my hand onto the table early, allowing for turn 2 Champion, turn 3 Champion, turn 4 Champion. There was a Master in there as well but he was dealt with. Tezzeret made an appearance, allowed me to dig for more answers, but he got dealt with as well. Couple of Tarmagoyfs here on the table but rendered useless by my Champions. Dispatched one of them, then held one back for blocking while the other two went in for the win.
4-1 (9-4)

So I'm onto the finals, and the Tarmagoyf is within my reach. All that stands between him and I is.....
Finals - Mike Giles (BW Tokens)
Mike's a very good player; very deliberate, plays very tightly. We've played a bit in the past, it's always been pleasant, he gives me deck tips and I always listen :). I've managed to get the upper hand on him a few times, but each time I'm always very lucky.
Game 1 - According to my notes, he hits token generators really quickly and decimates my robot army
SB - Can't remember, no notes, but probably similar to round 2 with no Despise
Game 2 - I get a nasty draw, and proceed to yak my hand onto the table with something to the effect of Inkmoth, Mox, Ornithopter, Drum, Memnite, Thoughtcast. By turn 3 I swung in for 9 poison damage with my Plated Inkmoth. Things were coming up Millhouse for me until Mike cast a Lingering Souls, allowing him to stabilize. It went downhill from there as I just couldn't keep up with the tokens
4-2 (9-6)

So I ended up in second, $20 in store credit. For a 12 person tourney, I'm very happy. I beat two really good players and took a ported deck to second place. Etched Champion was a house since no one could deal with it effectively (except for the Affinity player who could block it all day).

I think BU is the optimal build with Tezzeret. It has the explosiveness of Affinity, but can grind out a longer game with a resolved Tezzeret. He becomes an immediate threat since he'll end the game the next turn, and I'll usually have a Champion or two to help protect him.

Changes to the deck, I'd overhaul the SB completely. Ravager, Despise, and Parasite have to come out, with Disenchant coming in. Not sure of numbers, but at least one more card has to go in. As for the main, I ended up siding out Myr Enforcer a lot, so I would probably drop him altogether. He wasn't really a factor in most of my games, at most a decent blocker. Might put in some targeted removal.