If you want status changing effects (or just good cards to have in a
leaf deck), these are among the best you'll find. Heres the stats:

Koffing:
50 HP
2 leaf energies:foul gas- 10; flip a coin. If heads, the defending
pokemon is now Poisoned; if tails, it is now confused.
Weakness to psycic
No resistance
1 retreat

Weezing
60 HP
2 leaf energies: smog- 20; Flip a cion. If heads, the defending pokemon
is now poisoned.
2 leaf and a colorless: selfdestruct- 60; Does 10 damage to each pokemon
on each players bench (don't count weakness or resistance for them).
Weezing does 60 damage to itself.
Weakness to psycic
No resistance
one retreat

OK. If you use Koffing in a venusaur deck, you can get the two energies
you need for foul gas and then the defending pokemon is either confused
or poisoned. He has one retreat, so he is easy to move arould. His HP is
50 (pretty good for a basic) and he is common, so he isn't very hard to
get. His major weaknesses: high attacks and psycic attacks.

Weezing is totally different. He has 60 HP (not great) and a 20 attack
(needs 2 leaf; chance of poison) and a 60 attack (10 damage to each
pokemon on each players bench and Weezing does 60 damage to itself). For
smog, have 2 leaf energies on Koffing before you evolve it and you'll be
fine. For selfdestruct, you can put on a defender and you'll still live
to selfdestruct again! He also has one retreat and basically the same
weaknesses as Koffing. 

I hope you consider using these in your deck. They are quite useful and
underrated...