Painiac

At the beginning of your upkeep, roll a six-sided die. Painiac gets +X/+0 until end of turn, where X is the result.

Thriving Bluff

Thriving Bluff enters tapped. As it enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

Just Desserts

Just Desserts deals π damage to target creature. (π is the ratio of a circle's circumference to its diameter. (It's a smidgen more than 3.))

Mountain

Goblin Haberdasher

Menace (This creature can't be blocked except by two or more creatures.)
Other creatures you control wearing hats in their art have menace.

Strategy, Schmategy

Roll a six-sided die. Strategy, Schmategy has the indicated effect.
1 — Do nothing.
2 — Destroy all artifacts.
3 — Destroy all lands.
4 — Strategy, Schmategy deals 3 damage to each creature and each player.
5 — Each player discards their hand and draws seven cards.
6 — Repeat this process two more times.

Goblin Bookie

{R}, {T}: Reflip any coin or reroll any die. (Activate only any time it makes sense.)

Hammer Helper

Gain control of target creature until end of turn. Untap that creature and roll a six-sided die. Until end of turn, it gains haste and gets +X/+0, where X is the result.

Garbage Elemental

Last strike (This creature deals combat damage after creatures without last strike.)
Battalion — Whenever Garbage Elemental and at least two other creatures attack, target creature can't block this turn.

Underdome

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to pay Un-costs.

The Big Idea

{2}{B/R}{B/R}, {T}: Roll a six-sided die. Create a number of 1/1 red Brainiac creature tokens equal to the result.
Tap three untapped Brainiacs you control: The next time you would roll a six-sided die, instead roll two six-sided dice and use the total of those results.

Hammer Jammer

As Hammer Jammer enters, roll a six-sided die. Hammer Jammer enters with a number of +1/+1 counters on it equal to the result.
Whenever you roll a die, remove all +1/+1 counters from Hammer Jammer, then put a number of +1/+1 counters on it equal to the result.

Super-Duper Death Ray

Trample (This spell can deal excess damage to its target's controller.)
Super-Duper Death Ray deals 4 damage to target creature.

Abstract Iguanart

Whenever you cast a spell, note the first letter of its artist's name. If that letter wasn't already noted, put a +1/+1 counter on Abstract Iguanart.

Face to Face

You and target opponent play a best two-out-of-three Rock, Paper, Scissors match. If you win, Face to Face deals 5 damage to that player.