As others have pointed out, Absol's available movepool in the 3rd gen games is pitiful.
However, several factors introduced in the 4th gen games make Absol a much more formidable pokemon:
For one, the physical/special attack distinction for individual moves REALLY tips the odds more in Absol's favor.
Also, the inclusion of many powerful physical moves that Absol can be taught by a move tutor in Plat/HG/SS (Zen Headbutt, Bounce, Superpower), as well as moves that an Absol could be bred to have (most notable is MegaHorn - 120 physical bug move - breedable in HGSS only) give you a wider variety of options for Absol's moveset.
Finally, the ability Super Luck is an option for 4th gen Absols, which ups the critical hit ratio of moves. Coupled with new level up moves like Night Slash (dark physical move) and Psycho Cut (psychic physical move), both of which have 70 power and high critical hit ratios, Absol becomes a great pokemon for the main game.
I have successfully used an Adamant-Super Luck one in Pearl with the following move set:
Swords Dance
Night Slash
Psycho Cut
Slash
Given the fairly wide variety of move types Absol can learn through TMs, you can also do a set for handling many different type weaknesses. Absol can learn powerful physical moves like Shadow Claw (ghost-70 power-high crit. hit ratio), Stone Edge (rock-100 power), Iron Tail (steel-100 power) and X-Scissor (bug-80 power)(TM in Gen 4, Move Tutor in Gen 5), just to name a few.
Overall, I'd say he's great in the right game (4th gen and up).
Great to use for any in-game opponent (with the right moveset, of course), but I probably wouldn't use him against another player.
« Last edited by phoenragon on Aug 4th 2012 »