You could combine this card with the effects of Gagaga Magician, since it is able to select its own level (1-8) without requiring tribute, though the boost in attack points will only last until your End Phase.
You can use this card in combination with "Greed Quasar" and "Ancient Dragon" because "Greed Quasar" and "Ancient Dragon" can increase their own levels, and can reach levels exceeding 12.
By activating 3 "Metal Reflect Slimes" on the turn you summon this card, its ATK will be at least 9600 or more (if you have another monster on the field). If your opponent has no cards on his/her field, it'll be an OTK.
This card works well with "Tragoedia", since it is a Level 10 Monster, can Special Summon itself and change its Level.
This card fits in well in either a Fortune Lady or F.A. deck, since the two archetypes are focused around manipulating their own levels. .
If after normal summoning a "Fusilier Dragon, the Dual-Mode Beast" to the field using its effects, you reduce its ATK with "Shooting Star Bow - Ceal"; you can use "Machine Duplication" and get more "Fusilier Dragons". This will give you (2) 2800 ATK monsters, (1) 400 ATK monster that can direct-attack, and 6300 ATK-boost to "The Calculator" (6900 ATK points). In total, the ATK of all your monsters combined would be 12900, more than enough to OTK.
On a similar note, if you use the effect of "Junk Synchron" to bring this card back, it is then a legal target for "Inferno Reckless Summon", provided your opponent has a monster out. Then, you can Synchro Summon into "Junk Warrior", who will have an impressive 7700 attack points, with each of "The Calculator" at 2700 ATK.
The above can be a formation of a powerful FTK if you're going second. Discard "The Calculator" to Special Summon "Quickdraw Synchron", then do the above. This will result in 2 4200-ATK "The Calculators" and a 10,700 ATK "Junk Warrior".
This card is great in many swarm decks that use level 4 monsters, particularly Crystal Beasts, as it will benefit from the decent amount of total levels on the field from multiple monsters.
In addition, "Red-Eyes Darkness Metal Dragon" can power up this card further, since it can special summon itself and another high-level Dragon-Type Monster.
This card works well in a Fabled Deck. "Fabled Raven" is able to increase its own level and ATK by discarding cards. If you discard "The Fabled Cerburrel" or "Fabled Krus" by this effect, you will get another monster out to further increase this cards ATK.
This card should not be used with Effect cards that only modify attack and do not offer an effect. The effect of "The Calculator" ensures that its ATK is always equal to the combined levels of all monsters you control x300.
Use the first effect of "Magic Hole Golem" to allow this card to perform a direct attack. Because the ATK of "The Calculator" is always the total combined levels of all monsters you control x300, the second effect of "Magic Hole Golem" will not function and you can deal full damage to your opponent's Life Points. Use card effects like that of "Twin Swords of Flashing Light - Tryce" to double the damage further.
Use 3 "Tannhauser Gates" on 2 copies of Yubels to make 2 level 80 monsters, then use "Galaxy Queen's Light" with three "The Calculator" also on the field to have 5 Lv. 80 monsters (resulting in 3 "The Calculators" at 120,000 Atk each).
"Puppet Master's" effect can be useful with this card since it can special summon 2 Fiends from the graveyard.