I've been playing goblins in modern for quite a long time now, and i win a lot more than i should with a deck like this. Sometimes i fall victim to flooding screwing, but most of the times opponents aren't prepared against me and i destroy everyone. Last saturday i won a 20 people event, beating jund, affinity, affinity, draw into top 8, then beat bg rock, uw control, and split the final against martyr life which i could never have beaten. If i had all the fetches (i just own 3 arid mesas for modern), i would probably play red deck wins or 3 color burn, but i'm starting to think goblins is on par if not better than burn. My current list is :
[deck]
4 Goblin Guide
4 Foundry Street Denizen
4 Legion Loyalist
4 Lightning Bolt
4 Goblin Grenade
4 Spike Jester
4 Mogg War Marshal
4 Goblin Chieftain
4 Goblin Bushwhacker
1 Mogg Fanatic
1 Spikeshot Elder
1 Goblin King
4 Blood Crypt
4
Cavern of Souls
4 Auntie's Hovel
3 Arid Mesa
2 Blackcleave Cliffs
3 Mountain
1 Keldon Megaliths
[/deck]
Sideboard:
[deck]
4 Rakdos Charm
2 Blood Moon
2 Thoughtseize
2 Dismember
2 Shatterstorm
2 Shattering Spree
1 Rain of Gore[/deck]
I strongly advise splashing black. Essentially the splash is "free" because you have access to Auntie's Hovel, Cavern of Souls and Blackcleave Cliffs which basically have no drawback. Cavern doesn't let you cast burn spells or sideboard cards but you have enough colored sources (17) to make even a double colored non goblin card (rakdos charm is the only one) castable without many issues. I would always play some caverns because thay absolutely wreck decks with counterspells, giving you free wins when you have a cavern and they have some number of remand/mana leak/deprive/spell snare in hand. Actually being able to avoid counterspells is to me one of the best reasons to run this deck instead of burn or red deck wins.
The
one of keldon megaliths was included recently because i want a 21st land since i run 5 3 drops wich are quite essential to the deck... but in the end i could get off also with 20 lands so i'm fine having a come into play tapped mana source that can add reach or kill weenies. Before of megaliths i was running two mutavaults but i was having troubles with coloured sources, so i first cut to only one mutavault then switched to megaliths wich is better in my opinion.
The only main deck black card is Spike Jester, but men he is really worth the splash.... turn one guide turn 2 jester is game everytime they don't have an answer immediately.... 7 damages by turn 2 is too much to handle for almost any opponent. from the side rakdos charm is unbelievably good for its versatility, allowing you to have access to extra artifact removal against robots, hate cards against twin strategies, or grave hate. Thoughtseize is good but not fantastic.. it usually comes in against combo, control, or midrange decks with
sweepers, even if sometimes it creates awkward situations when you wish to topdeck a burn spell and you draw the discard spell instead. 4 discard spells are definitely too much i think, since you can't dilute creature count too much and you will never win without an explosive start. Dismember was combust before, but goyf can create problem so this is the answer (or Terminate if you prefer). Blood Moon doesn't need explanation , it wrecks opponents, just beware not having too much rakdos charms /spike jester/thoughtseize in your deck if you side in moon. Rain of gore and artifact hate are meta calls since my lgs always represents 2-3 affinity and the occasional soul sister (not that i have hope against it, but i believe in the one of rain of gore

)
Regarding main deck, i think the flexible slots are just the three one ofs. Everything else is needed to me.... at first i was a bit skeptical about 4 loyalists but you'll
be surprised how good it is against a lot of decks. Even when his abilities are not relevant at all, a raging goblin is decent int his deck. Khaos will disagree with not running 4 mogg fanatic, but i don't think this is the kind of deck where fanatic shines. You just want to race and if you don't win soon you won't win (well, sometimes games go long because you manage to get them at 5 life or less, then they just can't attack and you play draw go until you find a grenade/bolt and win.... but this doesn't change the fact that you need to heavily attack their life total immediately),and i usually don't want to waste my one drop to kill a mana dork because i need to race. Obviously more fanatics would be good against affinity or pestermites, but you can't have them all and i think is better to run cards that are functional to your main strategy. the only other kind of slow card is mogg war marshal, but he is a must to me because he provides more bodies against removal and combos nicely with foundry
street denizen and goblin grenade.... mogg war marshal is like our silvergill adept, because a 1/1 is like an extra card to us
What else to say.... i can't stress enough that you just race you mustn't oversideboard with this deck, because it works in a comboish manner. The first cards to come out are always a couple of goblin grenades, because they get worse with less goblins in the deck, then you start shaving the less efficients creatures.
Worst matchup is soul sisters for obvious reasons and affinity preboard, because the only realistic option is to race them and is often very difficult due to etched champion or vault skirge + cranial plating or they just race you although you are generally a bit faster. Midrange decks are even matchups , but overall i have a positive record against jund. Control decks are quite favourable especially if you have cavern of souls. Merfolk and G/W hatebears are a cakewalk.
Straight combo /ad nauseam, living end) is not as bad as it may seem because when undisrupted i always win by turn 4 and a decent number of times by turn 3. Twin is even. Pod is quite unfavourable due to voice of resurgence /persist creatures which are a beating for us.
Most problematic cards are electrolyze, kitchen finks, voice of resurgence. Sweepers are bad but not terribly bad because if they tap out sorcery speed then they are facing a deck with almost only haste creatures and burn spells, so you are able to deal damage immediately.
Shared Animosity is really win more.... you can play a one off but almost always you would prefer a creature to it. I lost more games than i won because of it.
Sorry for the long and boring post, but i just wanted to share everything i know about goblins in modern..... i could for sure add more but this is enough for now. And thanks to khaos for having opened this thread.