Here are a bunch:
Living Bomb +
Hellgrammite
If you survive with HP <= 20, both creatures die and you get a Serpent Fly on the territory. Can be used offensively or defensively (via armor or that killing tactic).
Mass Phantasm +
Exile +
Uriel
Let's you remove creatures who can't be targeted (and have no summoning conditions). Use Uriel to clean the board after.
Lunatic Hare +
Succubus Ring
A classic. Succubus Ring sets ST=0 on hit, and Hare swaps that to HP=0.
Battering Ram +
Turn to the Wall or
Cockatrice
Battering Ram instant kills the wall you get from the spell or Cockatrice on hit.
Thrust Blow +
Bird Maiden
Push a creature off of a high level land and use Bird Maiden (or a creature Bird Maiden enchanted) to move onto it. Can work well with Breeze Spirit or Dryad, etc.
Immobilize +
Nil-Vana +
Insect Swarm
More reliable mass damage sequence. With Immobilize, creatures can't move to remove the enchantment.
Vortex +
Rock Titan
Rock Titan is a printed 70/70 and will kill any creature without printed HP > 70.
General Guan +
Turn to the Wall or
Fat Body
Increase MHP of creatures so that General Guan gets a... fat bonus.
Powder Eater +
Fat Body
Duplicate higher HP PEs. Consider Bird Maiden so you can pop PEs off to any vacant land. Get enough of them out and Tiny Army will be a nice addition.
Thief +
Borgess
At MHP=60, she can only be taken down by creatures that can hit ST>=60 without items.
Doom Devourer +
Swamp Spawn +
Charging Step
Moving slowly pumps up Doom Devourer's stats.
Exchange +
Brontides
The best defender of the elemental lords, Exchange lets you summon him without meeting the discard and earth land costs. Of course, this works for any large creature (I see you, Massive Dragon)
Enchantress +
Metal Form
Give all of your creatures the Metallize enchantment. Be sure to sack Enchantress after else you opponent can use her against you.
Dwarven Miner +
Quicksand
Make an opponent stop and pay an enhanced toll.
Old Willow or
Kelpie +
Peace
Useful to screw with opponent movement. Some strategic uses are delaying opponent's lap bonus by a turn or keeping them from lapping or landing on a gate and standing their creatures.
Quintessence +
Holy Banishment
Return a (targetable) creature to its cepter's hand.
Waste World +
Life Force
Make everyone else pay more for creatures whilst yours are free of G cost. Works well with expensive breed dragons.
Baldanders +
Dragon Orb
Since there are two transformations Baldanders -> Random Creature -> Random Dragon, at the end of battle you'll keep the random creature. Hopefully it's something good!
Gremlin +
Living Amulet
Since Gremlin destroys every weapon card, if it gets killed it'll return as a Living Amulet.
Gremlin +
Mirror Hoplon
Makes Gremlin almost invincible. It's still susceptible to items that can't be destroyed.
Living Amulet +
Burning Heart
Great suicide combo to steal a land with when the opponent has no weapons and can naturally destroy Living Amulet.
Coatlicue +
Poison Mind
Tear your opponent's book apart using Coatlicue's spell and Poison Mind. She gets a nice stat boost out of it, too.
Nil-Vana +
Tyranny
Quickly damage creatures of MHP 30 and under. Nil-Vana is not subject to the enchantment, so it remains undamaged. If you have MHP >= 40 creatures, you won't suffer.
Lone Beast +
Fay
Use Fay to boost Lone Beast's base ST which gets added to his HP in battle. With just one use of Fay it'll have HP80 in battle.
Lone Beast +
Mad Harlequin
With Mad Harlequin in play, not only will Lone Beast get MH's 20/20+ boost if fighting next to an ally, but it'll get Critical Hit[All].
Lunatic Hare +
Angry Mask
If opponent's ST=0, they'll die at the end. If not, then Angry Mask will destroy them at the end of battle after ST and HP get swapped (if Hare survives).
Treasure Raider +
Debility (on a regenerating creature)
This combo let's you continually invade an adjacent territory and gain G100 each time.
Uniformity +
Peace
Enemy cepters can't invade your lands, but have to pay a G200 toll.
Sulfurous Balloon +
Necro Scarab
Use offensively to kill defending creature and steal the territory with a Skeleton.
Tetrarm +
Twin Spike
The first attack transforms the opponent into Tetrarm. Since item/land effects were already applied to the original opponent, the opponent Tetrarm has base stats and the second attack destroys them.
Tetrarm + Scroll Attack
Double scroll attack
Samhain (synthesized) +
Twin Spike
The first attack transforms the opponent into Samhain (non-synthesized). Since item/land effects were already applied to the original opponent, you'll survive the counterattack (at ST=20). At the end of battle the opponent receives MHP-40 (your base ST) and dies.
Powder Eater +
Twin Spike
Turn a big, hulking defender into a puny Powder Eater. If it's already Down, you may have a chance to steal the territory easily.
Leshy +
Outrage +
Twin Spike
You'll need Leshy to survive since it attacks last, but if it does you can pump the land level up by 2 and later reinvade against a Leshy to steal the territory. Alternatively, use Outrage to push a creature onto Leshy. It you can manage (say, with the control tower) summon Leshy next to a low ST enemy defensive creature and use the combo then.
Natural World +
Rock Titan or
Ba-Al
Natural World removes the inconvenient end of battle detriments.
Mirror World+
Shape Shifter (as a Doppelgänger)
If Shape Shifter is imitating a creature on the map (say, an adjacent creature), then you have a good suicide combo by moving them over to invade.
Joint World +
Chainsaw
Joint World can increase the chain the opponent's territory is a part of, thus strengthening
Foresight +
Sense of Wild
Foresight lets you see when you have a creature coming so you can use Sense of Wild for a guaranteed summon (Sense of Wild draws the top card of the book).
Triton +
Soul Ray
Triton draws a card every time it uses an item. Not only does Soul Ray return to the hand so he can keep using it, but he has scroll critical so you get an ST=45 scroll attack out of it. Boomerang also works (more cheaply, too).
Rune Adept +
Form Portal
This combo lets you jump from gate to gate, earning you the gate/lap bonuses and removing Down on all of your creatures. If no one has Speed Penalty, you can lap ultra fast, which is good for creatures like Dwarven Miner, Chimera, Amazon, Mummy, and the spell Manna.
Quintessence or
Stone Jizo +
Thunder Spawn
Turn an enemy territory into a non-elemental land so that Thunder Spawn can invade it from afar.
Decoy +
Living Bomb
A strong combo to almost certainly vacate an enemy territory.