I enjoy playing underdog decks, and have recently been trying Leopardmon in the BT8/EX2 meta. While this deck has some weaknesses against some tier-1 decks, it has managed very well against them, and may even pulverize many tier-1.5 or lower decks.
Leopardmon: not doing much
A card from the old days of BT3, Leopardmon is a very unpopular card. At 4-cost to digivolve, he is a very expensive LV6 Digimon that doesn't do much!
Yes he lets us play a LV4 (or lower) Digimon from a digivolution source for free, but theoretically the [On Play] effect of any LV4 Digimon should not be better than a LV6. In other words, he does not delete an opponent's Digimon, or trash their security, or blitz at them, or suspend the opponent's Digimon through their turn… nothing!
Recently in EX-02, Bandai gave us a new Gorillamon that is able to pull a LV3 Digimon from digivolution source, which could work well with Leopardmon. However, I do not see any LV3 worth pulling (other than Lucemon) that won't get itself deleted during the next turn, with the meta running so aggressive these days.
However, I wanted to believe that Leopardmon has some untapped potential in the form of his second effect. Leopardmon grants [Jamming] to your LV4 or lower Digimons, which is handsome thanks to the recently popular Jogress effects. When played properly, your LV4 Digimons can all swing at security before Jogress digivolving into LV5 hence making the most out of your turn.
My experimental build
The concept that I am using is straightforward: by using Kimeramon, I may be able to put 1 or 2 copies of [BT7-032] Pulsemon under its digivolution cards, which will swing for +4 memory (or +5 if inheriting Bibimon) when I have exactly 3 security cards. This deck performs best when there is exactly 3 memory, and slightly worse when it has less.
Since the deck relies on LV5 Jogress, it is imperative that LV4 Digimons can be deployed effectively and at will.
[BT6-036] Mimicmon is the cheapest LV4 to play when we have 3 security or less, while Tommy/Blizzarmon helps to slow the game down. Blizzarmon can also digivolve from Angemon for recovery at 1 cost, if that is ever needed.
I realised that navigating this deck requires a lot of forward looking, and timing is essential to generate value.
When there is nothing on your opponent's board, I would prep my nursery to Angemon, play cards like Sora & Joe or even hard-cast that Angemon. Once an opponent's Digimon is fielded, Tommy/Blizzarmon helps freeze the cards that I could deal with in the current turn.
At LV5, Kimeramon can easily gain 3 colors for a -3000 DP wipe, or 4 colors for -4000 DP if he is able to inherit Rapidmon. If I am at exactly 3 security, pulling another BT7 Pulsemon from trash into Kimeramon would help me swing for +4/+5 memory, enough to move into Leopardmon with some to spare. In addition, Leopardmon can pull Mimicmon for that +2 memory, making the entire chain pretty efficient.
Leopardmon can finally move into Omegamon when the game calls for a much-needed deletion, and prepping for 2 hits in his following turn, replenishing Leopardmon to your hand.
I am certainly enjoying this deck for now, and while I understand that is may not necessarily fare well against the meta decks of today, I merely wished to share a possibility that is the Pulsemon/Kimeramon engine with Leopardmon and Mimicmon.
Here is to a possibility of future sets strengthening this deck!